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a47a126ad5
Christoph recently added /proc/vmallocinfo file to get information about
vmalloc allocations.
This patch adds NUMA specific information, giving number of pages
allocated on each memory node.
This should help to check that vmalloc() is able to respect NUMA policies.
Example of output on a four nodes machine (one cpu per node)
1) network hash tables are evenly spreaded on four nodes (OK) (Same
point for inodes and dentries hash tables)
2) iptables tables (x_tables) are correctly allocated on each cpu node
(OK).
3) sys_swapon() allocates its memory from one node only.
4) each loaded module is using memory on one node.
Sysadmins could tune their setup to change points 3) and 4) if necessary.
grep "pages=" /proc/vmallocinfo
0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204/0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204/0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
0xffffc2000031a000-0xffffc2000031d000 12288 alloc_large_system_hash+0x204/0x2c0 pages=2 vmalloc N1=1 N2=1
0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e/0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
0xffffc2000033e000-0xffffc20000341000 12288 sys_swapon+0x640/0xac0 pages=2 vmalloc N0=2
0xffffc20000341000-0xffffc20000344000 12288 xt_alloc_table_info+0xfe/0x130 [x_tables] pages=2 vmalloc N0=2
0xffffc20000344000-0xffffc20000347000 12288 xt_alloc_table_info+0xfe/0x130 [x_tables] pages=2 vmalloc N1=2
0xffffc20000347000-0xffffc2000034a000 12288 xt_alloc_table_info+0xfe/0x130 [x_tables] pages=2 vmalloc N2=2
0xffffc2000034a000-0xffffc2000034d000 12288 xt_alloc_table_info+0xfe/0x130 [x_tables] pages=2 vmalloc N3=2
0xffffc20004381000-0xffffc20004402000 528384 alloc_large_system_hash+0x204/0x2c0 pages=128 vmalloc N0=32 N1=32 N2=32 N3=32
0xffffc20004402000-0xffffc20004803000 4198400 alloc_large_system_hash+0x204/0x2c0 pages=1024 vmalloc vpages N0=256 N1=256 N2=256 N3=256
0xffffc20004803000-0xffffc20004904000 1052672 alloc_large_system_hash+0x204/0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
0xffffc20004904000-0xffffc20004bec000 3047424 sys_swapon+0x640/0xac0 pages=743 vmalloc vpages N0=743
0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 pages=14 vmalloc N1=14
0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 pages=4 vmalloc N0=4
0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 pages=2 vmalloc N0=2
0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 pages=10 vmalloc N1=10
0xffffffffa0022000-0xffffffffa0028000 24576 sys_init_module+0xc27/0x1d00 pages=5 vmalloc N3=5
0xffffffffa0028000-0xffffffffa0050000 163840 sys_init_module+0xc27/0x1d00 pages=39 vmalloc N1=39
0xffffffffa0050000-0xffffffffa0052000 8192 sys_init_module+0xc27/0x1d00 pages=1 vmalloc N1=1
0xffffffffa0052000-0xffffffffa0056000 16384 sys_init_module+0xc27/0x1d00 pages=3 vmalloc N1=3
0xffffffffa0056000-0xffffffffa0081000 176128 sys_init_module+0xc27/0x1d00 pages=42 vmalloc N3=42
0xffffffffa0081000-0xffffffffa00ae000 184320 sys_init_module+0xc27/0x1d00 pages=44 vmalloc N3=44
0xffffffffa00ae000-0xffffffffa00b1000 12288 sys_init_module+0xc27/0x1d00 pages=2 vmalloc N3=2
0xffffffffa00b1000-0xffffffffa00b9000 32768 sys_init_module+0xc27/0x1d00 pages=7 vmalloc N0=7
0xffffffffa00b9000-0xffffffffa00c4000 45056 sys_init_module+0xc27/0x1d00 pages=10 vmalloc N3=10
0xffffffffa00c6000-0xffffffffa00e0000 106496 sys_init_module+0xc27/0x1d00 pages=25 vmalloc N2=25
0xffffffffa00e0000-0xffffffffa00f1000 69632 sys_init_module+0xc27/0x1d00 pages=16 vmalloc N2=16
0xffffffffa00f1000-0xffffffffa00f4000 12288 sys_init_module+0xc27/0x1d00 pages=2 vmalloc N3=2
0xffffffffa00f4000-0xffffffffa00f7000 12288 sys_init_module+0xc27/0x1d00 pages=2 vmalloc N3=2
[akpm@linux-foundation.org: fix comment]
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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------------------------------------------------------------------------------
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T H E /proc F I L E S Y S T E M
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------------------------------------------------------------------------------
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/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999
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Bodo Bauer <bb@ricochet.net>
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2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
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------------------------------------------------------------------------------
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Version 1.3 Kernel version 2.2.12
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Kernel version 2.4.0-test11-pre4
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------------------------------------------------------------------------------
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Table of Contents
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-----------------
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0 Preface
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0.1 Introduction/Credits
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0.2 Legal Stuff
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1 Collecting System Information
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1.1 Process-Specific Subdirectories
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1.2 Kernel data
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1.3 IDE devices in /proc/ide
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1.4 Networking info in /proc/net
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1.5 SCSI info
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1.6 Parallel port info in /proc/parport
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1.7 TTY info in /proc/tty
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1.8 Miscellaneous kernel statistics in /proc/stat
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2 Modifying System Parameters
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2.1 /proc/sys/fs - File system data
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2.2 /proc/sys/fs/binfmt_misc - Miscellaneous binary formats
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2.3 /proc/sys/kernel - general kernel parameters
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2.4 /proc/sys/vm - The virtual memory subsystem
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2.5 /proc/sys/dev - Device specific parameters
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2.6 /proc/sys/sunrpc - Remote procedure calls
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2.7 /proc/sys/net - Networking stuff
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2.8 /proc/sys/net/ipv4 - IPV4 settings
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2.9 Appletalk
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2.10 IPX
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2.11 /proc/sys/fs/mqueue - POSIX message queues filesystem
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2.12 /proc/<pid>/oom_adj - Adjust the oom-killer score
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2.13 /proc/<pid>/oom_score - Display current oom-killer score
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2.14 /proc/<pid>/io - Display the IO accounting fields
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2.15 /proc/<pid>/coredump_filter - Core dump filtering settings
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2.16 /proc/<pid>/mountinfo - Information about mounts
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------------------------------------------------------------------------------
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Preface
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------------------------------------------------------------------------------
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0.1 Introduction/Credits
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------------------------
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This documentation is part of a soon (or so we hope) to be released book on
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the SuSE Linux distribution. As there is no complete documentation for the
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/proc file system and we've used many freely available sources to write these
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chapters, it seems only fair to give the work back to the Linux community.
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This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
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afraid it's still far from complete, but we hope it will be useful. As far as
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we know, it is the first 'all-in-one' document about the /proc file system. It
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is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
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SPARC, AXP, etc., features, you probably won't find what you are looking for.
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It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
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additions and patches are welcome and will be added to this document if you
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mail them to Bodo.
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We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
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other people for help compiling this documentation. We'd also like to extend a
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special thank you to Andi Kleen for documentation, which we relied on heavily
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to create this document, as well as the additional information he provided.
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Thanks to everybody else who contributed source or docs to the Linux kernel
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and helped create a great piece of software... :)
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If you have any comments, corrections or additions, please don't hesitate to
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contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
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document.
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The latest version of this document is available online at
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http://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version.
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If the above direction does not works for you, ypu could try the kernel
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mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
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comandante@zaralinux.com.
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0.2 Legal Stuff
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---------------
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We don't guarantee the correctness of this document, and if you come to us
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complaining about how you screwed up your system because of incorrect
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documentation, we won't feel responsible...
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------------------------------------------------------------------------------
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CHAPTER 1: COLLECTING SYSTEM INFORMATION
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------------------------------------------------------------------------------
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------------------------------------------------------------------------------
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In This Chapter
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------------------------------------------------------------------------------
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* Investigating the properties of the pseudo file system /proc and its
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ability to provide information on the running Linux system
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* Examining /proc's structure
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* Uncovering various information about the kernel and the processes running
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on the system
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------------------------------------------------------------------------------
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The proc file system acts as an interface to internal data structures in the
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kernel. It can be used to obtain information about the system and to change
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certain kernel parameters at runtime (sysctl).
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First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
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show you how you can use /proc/sys to change settings.
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1.1 Process-Specific Subdirectories
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-----------------------------------
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The directory /proc contains (among other things) one subdirectory for each
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process running on the system, which is named after the process ID (PID).
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The link self points to the process reading the file system. Each process
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subdirectory has the entries listed in Table 1-1.
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Table 1-1: Process specific entries in /proc
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..............................................................................
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File Content
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clear_refs Clears page referenced bits shown in smaps output
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cmdline Command line arguments
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cpu Current and last cpu in which it was executed (2.4)(smp)
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cwd Link to the current working directory
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environ Values of environment variables
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exe Link to the executable of this process
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fd Directory, which contains all file descriptors
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maps Memory maps to executables and library files (2.4)
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mem Memory held by this process
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root Link to the root directory of this process
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stat Process status
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statm Process memory status information
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status Process status in human readable form
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wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
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smaps Extension based on maps, the rss size for each mapped file
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..............................................................................
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For example, to get the status information of a process, all you have to do is
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read the file /proc/PID/status:
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>cat /proc/self/status
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Name: cat
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State: R (running)
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Pid: 5452
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PPid: 743
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TracerPid: 0 (2.4)
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Uid: 501 501 501 501
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Gid: 100 100 100 100
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Groups: 100 14 16
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VmSize: 1112 kB
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VmLck: 0 kB
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VmRSS: 348 kB
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VmData: 24 kB
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VmStk: 12 kB
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VmExe: 8 kB
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VmLib: 1044 kB
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SigPnd: 0000000000000000
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SigBlk: 0000000000000000
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SigIgn: 0000000000000000
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SigCgt: 0000000000000000
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CapInh: 00000000fffffeff
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CapPrm: 0000000000000000
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CapEff: 0000000000000000
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This shows you nearly the same information you would get if you viewed it with
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the ps command. In fact, ps uses the proc file system to obtain its
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information. The statm file contains more detailed information about the
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process memory usage. Its seven fields are explained in Table 1-2. The stat
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file contains details information about the process itself. Its fields are
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explained in Table 1-3.
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Table 1-2: Contents of the statm files (as of 2.6.8-rc3)
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..............................................................................
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Field Content
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size total program size (pages) (same as VmSize in status)
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resident size of memory portions (pages) (same as VmRSS in status)
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shared number of pages that are shared (i.e. backed by a file)
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trs number of pages that are 'code' (not including libs; broken,
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includes data segment)
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lrs number of pages of library (always 0 on 2.6)
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drs number of pages of data/stack (including libs; broken,
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includes library text)
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dt number of dirty pages (always 0 on 2.6)
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..............................................................................
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Table 1-3: Contents of the stat files (as of 2.6.22-rc3)
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..............................................................................
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Field Content
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pid process id
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tcomm filename of the executable
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state state (R is running, S is sleeping, D is sleeping in an
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uninterruptible wait, Z is zombie, T is traced or stopped)
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ppid process id of the parent process
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pgrp pgrp of the process
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sid session id
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tty_nr tty the process uses
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tty_pgrp pgrp of the tty
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flags task flags
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min_flt number of minor faults
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cmin_flt number of minor faults with child's
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maj_flt number of major faults
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cmaj_flt number of major faults with child's
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utime user mode jiffies
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stime kernel mode jiffies
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cutime user mode jiffies with child's
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cstime kernel mode jiffies with child's
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priority priority level
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nice nice level
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num_threads number of threads
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it_real_value (obsolete, always 0)
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start_time time the process started after system boot
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vsize virtual memory size
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rss resident set memory size
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rsslim current limit in bytes on the rss
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start_code address above which program text can run
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end_code address below which program text can run
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start_stack address of the start of the stack
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esp current value of ESP
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eip current value of EIP
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pending bitmap of pending signals (obsolete)
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blocked bitmap of blocked signals (obsolete)
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sigign bitmap of ignored signals (obsolete)
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sigcatch bitmap of catched signals (obsolete)
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wchan address where process went to sleep
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0 (place holder)
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0 (place holder)
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exit_signal signal to send to parent thread on exit
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task_cpu which CPU the task is scheduled on
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rt_priority realtime priority
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policy scheduling policy (man sched_setscheduler)
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blkio_ticks time spent waiting for block IO
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..............................................................................
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1.2 Kernel data
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---------------
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Similar to the process entries, the kernel data files give information about
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the running kernel. The files used to obtain this information are contained in
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/proc and are listed in Table 1-4. Not all of these will be present in your
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system. It depends on the kernel configuration and the loaded modules, which
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files are there, and which are missing.
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Table 1-4: Kernel info in /proc
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..............................................................................
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File Content
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apm Advanced power management info
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buddyinfo Kernel memory allocator information (see text) (2.5)
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bus Directory containing bus specific information
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cmdline Kernel command line
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cpuinfo Info about the CPU
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devices Available devices (block and character)
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dma Used DMS channels
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filesystems Supported filesystems
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driver Various drivers grouped here, currently rtc (2.4)
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execdomains Execdomains, related to security (2.4)
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fb Frame Buffer devices (2.4)
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fs File system parameters, currently nfs/exports (2.4)
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ide Directory containing info about the IDE subsystem
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interrupts Interrupt usage
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iomem Memory map (2.4)
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ioports I/O port usage
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irq Masks for irq to cpu affinity (2.4)(smp?)
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isapnp ISA PnP (Plug&Play) Info (2.4)
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kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
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kmsg Kernel messages
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ksyms Kernel symbol table
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loadavg Load average of last 1, 5 & 15 minutes
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locks Kernel locks
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meminfo Memory info
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misc Miscellaneous
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modules List of loaded modules
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mounts Mounted filesystems
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net Networking info (see text)
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partitions Table of partitions known to the system
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pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
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decoupled by lspci (2.4)
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rtc Real time clock
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scsi SCSI info (see text)
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slabinfo Slab pool info
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stat Overall statistics
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swaps Swap space utilization
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sys See chapter 2
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sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
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tty Info of tty drivers
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uptime System uptime
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version Kernel version
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video bttv info of video resources (2.4)
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vmallocinfo Show vmalloced areas
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..............................................................................
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You can, for example, check which interrupts are currently in use and what
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they are used for by looking in the file /proc/interrupts:
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> cat /proc/interrupts
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CPU0
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0: 8728810 XT-PIC timer
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1: 895 XT-PIC keyboard
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2: 0 XT-PIC cascade
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3: 531695 XT-PIC aha152x
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4: 2014133 XT-PIC serial
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5: 44401 XT-PIC pcnet_cs
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8: 2 XT-PIC rtc
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11: 8 XT-PIC i82365
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12: 182918 XT-PIC PS/2 Mouse
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13: 1 XT-PIC fpu
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14: 1232265 XT-PIC ide0
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15: 7 XT-PIC ide1
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NMI: 0
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In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
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output of a SMP machine):
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> cat /proc/interrupts
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CPU0 CPU1
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0: 1243498 1214548 IO-APIC-edge timer
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1: 8949 8958 IO-APIC-edge keyboard
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2: 0 0 XT-PIC cascade
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5: 11286 10161 IO-APIC-edge soundblaster
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8: 1 0 IO-APIC-edge rtc
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9: 27422 27407 IO-APIC-edge 3c503
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12: 113645 113873 IO-APIC-edge PS/2 Mouse
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13: 0 0 XT-PIC fpu
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14: 22491 24012 IO-APIC-edge ide0
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15: 2183 2415 IO-APIC-edge ide1
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17: 30564 30414 IO-APIC-level eth0
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18: 177 164 IO-APIC-level bttv
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NMI: 2457961 2457959
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LOC: 2457882 2457881
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ERR: 2155
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NMI is incremented in this case because every timer interrupt generates a NMI
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(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
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LOC is the local interrupt counter of the internal APIC of every CPU.
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ERR is incremented in the case of errors in the IO-APIC bus (the bus that
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connects the CPUs in a SMP system. This means that an error has been detected,
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the IO-APIC automatically retry the transmission, so it should not be a big
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problem, but you should read the SMP-FAQ.
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In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
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/proc/interrupts to display every IRQ vector in use by the system, not
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just those considered 'most important'. The new vectors are:
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THR -- interrupt raised when a machine check threshold counter
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(typically counting ECC corrected errors of memory or cache) exceeds
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a configurable threshold. Only available on some systems.
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TRM -- a thermal event interrupt occurs when a temperature threshold
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has been exceeded for the CPU. This interrupt may also be generated
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when the temperature drops back to normal.
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SPU -- a spurious interrupt is some interrupt that was raised then lowered
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by some IO device before it could be fully processed by the APIC. Hence
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the APIC sees the interrupt but does not know what device it came from.
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For this case the APIC will generate the interrupt with a IRQ vector
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of 0xff. This might also be generated by chipset bugs.
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RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
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sent from one CPU to another per the needs of the OS. Typically,
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their statistics are used by kernel developers and interested users to
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determine the occurance of interrupt of the given type.
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The above IRQ vectors are displayed only when relevent. For example,
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the threshold vector does not exist on x86_64 platforms. Others are
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suppressed when the system is a uniprocessor. As of this writing, only
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i386 and x86_64 platforms support the new IRQ vector displays.
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|
|
Of some interest is the introduction of the /proc/irq directory to 2.4.
|
|
It could be used to set IRQ to CPU affinity, this means that you can "hook" an
|
|
IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
|
|
irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
|
|
prof_cpu_mask.
|
|
|
|
For example
|
|
> ls /proc/irq/
|
|
0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
|
|
1 11 13 15 17 19 3 5 7 9 default_smp_affinity
|
|
> ls /proc/irq/0/
|
|
smp_affinity
|
|
|
|
smp_affinity is a bitmask, in which you can specify which CPUs can handle the
|
|
IRQ, you can set it by doing:
|
|
|
|
> echo 1 > /proc/irq/10/smp_affinity
|
|
|
|
This means that only the first CPU will handle the IRQ, but you can also echo
|
|
5 which means that only the first and fourth CPU can handle the IRQ.
|
|
|
|
The contents of each smp_affinity file is the same by default:
|
|
|
|
> cat /proc/irq/0/smp_affinity
|
|
ffffffff
|
|
|
|
The default_smp_affinity mask applies to all non-active IRQs, which are the
|
|
IRQs which have not yet been allocated/activated, and hence which lack a
|
|
/proc/irq/[0-9]* directory.
|
|
|
|
prof_cpu_mask specifies which CPUs are to be profiled by the system wide
|
|
profiler. Default value is ffffffff (all cpus).
|
|
|
|
The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
|
|
between all the CPUs which are allowed to handle it. As usual the kernel has
|
|
more info than you and does a better job than you, so the defaults are the
|
|
best choice for almost everyone.
|
|
|
|
There are three more important subdirectories in /proc: net, scsi, and sys.
|
|
The general rule is that the contents, or even the existence of these
|
|
directories, depend on your kernel configuration. If SCSI is not enabled, the
|
|
directory scsi may not exist. The same is true with the net, which is there
|
|
only when networking support is present in the running kernel.
|
|
|
|
The slabinfo file gives information about memory usage at the slab level.
|
|
Linux uses slab pools for memory management above page level in version 2.2.
|
|
Commonly used objects have their own slab pool (such as network buffers,
|
|
directory cache, and so on).
|
|
|
|
..............................................................................
|
|
|
|
> cat /proc/buddyinfo
|
|
|
|
Node 0, zone DMA 0 4 5 4 4 3 ...
|
|
Node 0, zone Normal 1 0 0 1 101 8 ...
|
|
Node 0, zone HighMem 2 0 0 1 1 0 ...
|
|
|
|
Memory fragmentation is a problem under some workloads, and buddyinfo is a
|
|
useful tool for helping diagnose these problems. Buddyinfo will give you a
|
|
clue as to how big an area you can safely allocate, or why a previous
|
|
allocation failed.
|
|
|
|
Each column represents the number of pages of a certain order which are
|
|
available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
|
|
ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
|
|
available in ZONE_NORMAL, etc...
|
|
|
|
..............................................................................
|
|
|
|
meminfo:
|
|
|
|
Provides information about distribution and utilization of memory. This
|
|
varies by architecture and compile options. The following is from a
|
|
16GB PIII, which has highmem enabled. You may not have all of these fields.
|
|
|
|
> cat /proc/meminfo
|
|
|
|
|
|
MemTotal: 16344972 kB
|
|
MemFree: 13634064 kB
|
|
Buffers: 3656 kB
|
|
Cached: 1195708 kB
|
|
SwapCached: 0 kB
|
|
Active: 891636 kB
|
|
Inactive: 1077224 kB
|
|
HighTotal: 15597528 kB
|
|
HighFree: 13629632 kB
|
|
LowTotal: 747444 kB
|
|
LowFree: 4432 kB
|
|
SwapTotal: 0 kB
|
|
SwapFree: 0 kB
|
|
Dirty: 968 kB
|
|
Writeback: 0 kB
|
|
AnonPages: 861800 kB
|
|
Mapped: 280372 kB
|
|
Slab: 284364 kB
|
|
SReclaimable: 159856 kB
|
|
SUnreclaim: 124508 kB
|
|
PageTables: 24448 kB
|
|
NFS_Unstable: 0 kB
|
|
Bounce: 0 kB
|
|
WritebackTmp: 0 kB
|
|
CommitLimit: 7669796 kB
|
|
Committed_AS: 100056 kB
|
|
VmallocTotal: 112216 kB
|
|
VmallocUsed: 428 kB
|
|
VmallocChunk: 111088 kB
|
|
|
|
MemTotal: Total usable ram (i.e. physical ram minus a few reserved
|
|
bits and the kernel binary code)
|
|
MemFree: The sum of LowFree+HighFree
|
|
Buffers: Relatively temporary storage for raw disk blocks
|
|
shouldn't get tremendously large (20MB or so)
|
|
Cached: in-memory cache for files read from the disk (the
|
|
pagecache). Doesn't include SwapCached
|
|
SwapCached: Memory that once was swapped out, is swapped back in but
|
|
still also is in the swapfile (if memory is needed it
|
|
doesn't need to be swapped out AGAIN because it is already
|
|
in the swapfile. This saves I/O)
|
|
Active: Memory that has been used more recently and usually not
|
|
reclaimed unless absolutely necessary.
|
|
Inactive: Memory which has been less recently used. It is more
|
|
eligible to be reclaimed for other purposes
|
|
HighTotal:
|
|
HighFree: Highmem is all memory above ~860MB of physical memory
|
|
Highmem areas are for use by userspace programs, or
|
|
for the pagecache. The kernel must use tricks to access
|
|
this memory, making it slower to access than lowmem.
|
|
LowTotal:
|
|
LowFree: Lowmem is memory which can be used for everything that
|
|
highmem can be used for, but it is also available for the
|
|
kernel's use for its own data structures. Among many
|
|
other things, it is where everything from the Slab is
|
|
allocated. Bad things happen when you're out of lowmem.
|
|
SwapTotal: total amount of swap space available
|
|
SwapFree: Memory which has been evicted from RAM, and is temporarily
|
|
on the disk
|
|
Dirty: Memory which is waiting to get written back to the disk
|
|
Writeback: Memory which is actively being written back to the disk
|
|
AnonPages: Non-file backed pages mapped into userspace page tables
|
|
Mapped: files which have been mmaped, such as libraries
|
|
Slab: in-kernel data structures cache
|
|
SReclaimable: Part of Slab, that might be reclaimed, such as caches
|
|
SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
|
|
PageTables: amount of memory dedicated to the lowest level of page
|
|
tables.
|
|
NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
|
|
storage
|
|
Bounce: Memory used for block device "bounce buffers"
|
|
WritebackTmp: Memory used by FUSE for temporary writeback buffers
|
|
CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
|
|
this is the total amount of memory currently available to
|
|
be allocated on the system. This limit is only adhered to
|
|
if strict overcommit accounting is enabled (mode 2 in
|
|
'vm.overcommit_memory').
|
|
The CommitLimit is calculated with the following formula:
|
|
CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
|
|
For example, on a system with 1G of physical RAM and 7G
|
|
of swap with a `vm.overcommit_ratio` of 30 it would
|
|
yield a CommitLimit of 7.3G.
|
|
For more details, see the memory overcommit documentation
|
|
in vm/overcommit-accounting.
|
|
Committed_AS: The amount of memory presently allocated on the system.
|
|
The committed memory is a sum of all of the memory which
|
|
has been allocated by processes, even if it has not been
|
|
"used" by them as of yet. A process which malloc()'s 1G
|
|
of memory, but only touches 300M of it will only show up
|
|
as using 300M of memory even if it has the address space
|
|
allocated for the entire 1G. This 1G is memory which has
|
|
been "committed" to by the VM and can be used at any time
|
|
by the allocating application. With strict overcommit
|
|
enabled on the system (mode 2 in 'vm.overcommit_memory'),
|
|
allocations which would exceed the CommitLimit (detailed
|
|
above) will not be permitted. This is useful if one needs
|
|
to guarantee that processes will not fail due to lack of
|
|
memory once that memory has been successfully allocated.
|
|
VmallocTotal: total size of vmalloc memory area
|
|
VmallocUsed: amount of vmalloc area which is used
|
|
VmallocChunk: largest contigious block of vmalloc area which is free
|
|
|
|
..............................................................................
|
|
|
|
vmallocinfo:
|
|
|
|
Provides information about vmalloced/vmaped areas. One line per area,
|
|
containing the virtual address range of the area, size in bytes,
|
|
caller information of the creator, and optional information depending
|
|
on the kind of area :
|
|
|
|
pages=nr number of pages
|
|
phys=addr if a physical address was specified
|
|
ioremap I/O mapping (ioremap() and friends)
|
|
vmalloc vmalloc() area
|
|
vmap vmap()ed pages
|
|
user VM_USERMAP area
|
|
vpages buffer for pages pointers was vmalloced (huge area)
|
|
N<node>=nr (Only on NUMA kernels)
|
|
Number of pages allocated on memory node <node>
|
|
|
|
> cat /proc/vmallocinfo
|
|
0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
|
|
/0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
|
|
0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
|
|
/0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
|
|
0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
|
|
phys=7fee8000 ioremap
|
|
0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
|
|
phys=7fee7000 ioremap
|
|
0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
|
|
0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
|
|
/0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
|
|
0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
|
|
pages=2 vmalloc N1=2
|
|
0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
|
|
/0x130 [x_tables] pages=4 vmalloc N0=4
|
|
0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
|
|
pages=14 vmalloc N2=14
|
|
0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
|
|
pages=4 vmalloc N1=4
|
|
0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
|
|
pages=2 vmalloc N1=2
|
|
0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
|
|
pages=10 vmalloc N0=10
|
|
|
|
1.3 IDE devices in /proc/ide
|
|
----------------------------
|
|
|
|
The subdirectory /proc/ide contains information about all IDE devices of which
|
|
the kernel is aware. There is one subdirectory for each IDE controller, the
|
|
file drivers and a link for each IDE device, pointing to the device directory
|
|
in the controller specific subtree.
|
|
|
|
The file drivers contains general information about the drivers used for the
|
|
IDE devices:
|
|
|
|
> cat /proc/ide/drivers
|
|
ide-cdrom version 4.53
|
|
ide-disk version 1.08
|
|
|
|
More detailed information can be found in the controller specific
|
|
subdirectories. These are named ide0, ide1 and so on. Each of these
|
|
directories contains the files shown in table 1-5.
|
|
|
|
|
|
Table 1-5: IDE controller info in /proc/ide/ide?
|
|
..............................................................................
|
|
File Content
|
|
channel IDE channel (0 or 1)
|
|
config Configuration (only for PCI/IDE bridge)
|
|
mate Mate name
|
|
model Type/Chipset of IDE controller
|
|
..............................................................................
|
|
|
|
Each device connected to a controller has a separate subdirectory in the
|
|
controllers directory. The files listed in table 1-6 are contained in these
|
|
directories.
|
|
|
|
|
|
Table 1-6: IDE device information
|
|
..............................................................................
|
|
File Content
|
|
cache The cache
|
|
capacity Capacity of the medium (in 512Byte blocks)
|
|
driver driver and version
|
|
geometry physical and logical geometry
|
|
identify device identify block
|
|
media media type
|
|
model device identifier
|
|
settings device setup
|
|
smart_thresholds IDE disk management thresholds
|
|
smart_values IDE disk management values
|
|
..............................................................................
|
|
|
|
The most interesting file is settings. This file contains a nice overview of
|
|
the drive parameters:
|
|
|
|
# cat /proc/ide/ide0/hda/settings
|
|
name value min max mode
|
|
---- ----- --- --- ----
|
|
bios_cyl 526 0 65535 rw
|
|
bios_head 255 0 255 rw
|
|
bios_sect 63 0 63 rw
|
|
breada_readahead 4 0 127 rw
|
|
bswap 0 0 1 r
|
|
file_readahead 72 0 2097151 rw
|
|
io_32bit 0 0 3 rw
|
|
keepsettings 0 0 1 rw
|
|
max_kb_per_request 122 1 127 rw
|
|
multcount 0 0 8 rw
|
|
nice1 1 0 1 rw
|
|
nowerr 0 0 1 rw
|
|
pio_mode write-only 0 255 w
|
|
slow 0 0 1 rw
|
|
unmaskirq 0 0 1 rw
|
|
using_dma 0 0 1 rw
|
|
|
|
|
|
1.4 Networking info in /proc/net
|
|
--------------------------------
|
|
|
|
The subdirectory /proc/net follows the usual pattern. Table 1-6 shows the
|
|
additional values you get for IP version 6 if you configure the kernel to
|
|
support this. Table 1-7 lists the files and their meaning.
|
|
|
|
|
|
Table 1-6: IPv6 info in /proc/net
|
|
..............................................................................
|
|
File Content
|
|
udp6 UDP sockets (IPv6)
|
|
tcp6 TCP sockets (IPv6)
|
|
raw6 Raw device statistics (IPv6)
|
|
igmp6 IP multicast addresses, which this host joined (IPv6)
|
|
if_inet6 List of IPv6 interface addresses
|
|
ipv6_route Kernel routing table for IPv6
|
|
rt6_stats Global IPv6 routing tables statistics
|
|
sockstat6 Socket statistics (IPv6)
|
|
snmp6 Snmp data (IPv6)
|
|
..............................................................................
|
|
|
|
|
|
Table 1-7: Network info in /proc/net
|
|
..............................................................................
|
|
File Content
|
|
arp Kernel ARP table
|
|
dev network devices with statistics
|
|
dev_mcast the Layer2 multicast groups a device is listening too
|
|
(interface index, label, number of references, number of bound
|
|
addresses).
|
|
dev_stat network device status
|
|
ip_fwchains Firewall chain linkage
|
|
ip_fwnames Firewall chain names
|
|
ip_masq Directory containing the masquerading tables
|
|
ip_masquerade Major masquerading table
|
|
netstat Network statistics
|
|
raw raw device statistics
|
|
route Kernel routing table
|
|
rpc Directory containing rpc info
|
|
rt_cache Routing cache
|
|
snmp SNMP data
|
|
sockstat Socket statistics
|
|
tcp TCP sockets
|
|
tr_rif Token ring RIF routing table
|
|
udp UDP sockets
|
|
unix UNIX domain sockets
|
|
wireless Wireless interface data (Wavelan etc)
|
|
igmp IP multicast addresses, which this host joined
|
|
psched Global packet scheduler parameters.
|
|
netlink List of PF_NETLINK sockets
|
|
ip_mr_vifs List of multicast virtual interfaces
|
|
ip_mr_cache List of multicast routing cache
|
|
..............................................................................
|
|
|
|
You can use this information to see which network devices are available in
|
|
your system and how much traffic was routed over those devices:
|
|
|
|
> cat /proc/net/dev
|
|
Inter-|Receive |[...
|
|
face |bytes packets errs drop fifo frame compressed multicast|[...
|
|
lo: 908188 5596 0 0 0 0 0 0 [...
|
|
ppp0:15475140 20721 410 0 0 410 0 0 [...
|
|
eth0: 614530 7085 0 0 0 0 0 1 [...
|
|
|
|
...] Transmit
|
|
...] bytes packets errs drop fifo colls carrier compressed
|
|
...] 908188 5596 0 0 0 0 0 0
|
|
...] 1375103 17405 0 0 0 0 0 0
|
|
...] 1703981 5535 0 0 0 3 0 0
|
|
|
|
In addition, each Channel Bond interface has it's own directory. For
|
|
example, the bond0 device will have a directory called /proc/net/bond0/.
|
|
It will contain information that is specific to that bond, such as the
|
|
current slaves of the bond, the link status of the slaves, and how
|
|
many times the slaves link has failed.
|
|
|
|
1.5 SCSI info
|
|
-------------
|
|
|
|
If you have a SCSI host adapter in your system, you'll find a subdirectory
|
|
named after the driver for this adapter in /proc/scsi. You'll also see a list
|
|
of all recognized SCSI devices in /proc/scsi:
|
|
|
|
>cat /proc/scsi/scsi
|
|
Attached devices:
|
|
Host: scsi0 Channel: 00 Id: 00 Lun: 00
|
|
Vendor: IBM Model: DGHS09U Rev: 03E0
|
|
Type: Direct-Access ANSI SCSI revision: 03
|
|
Host: scsi0 Channel: 00 Id: 06 Lun: 00
|
|
Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
|
|
Type: CD-ROM ANSI SCSI revision: 02
|
|
|
|
|
|
The directory named after the driver has one file for each adapter found in
|
|
the system. These files contain information about the controller, including
|
|
the used IRQ and the IO address range. The amount of information shown is
|
|
dependent on the adapter you use. The example shows the output for an Adaptec
|
|
AHA-2940 SCSI adapter:
|
|
|
|
> cat /proc/scsi/aic7xxx/0
|
|
|
|
Adaptec AIC7xxx driver version: 5.1.19/3.2.4
|
|
Compile Options:
|
|
TCQ Enabled By Default : Disabled
|
|
AIC7XXX_PROC_STATS : Disabled
|
|
AIC7XXX_RESET_DELAY : 5
|
|
Adapter Configuration:
|
|
SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
|
|
Ultra Wide Controller
|
|
PCI MMAPed I/O Base: 0xeb001000
|
|
Adapter SEEPROM Config: SEEPROM found and used.
|
|
Adaptec SCSI BIOS: Enabled
|
|
IRQ: 10
|
|
SCBs: Active 0, Max Active 2,
|
|
Allocated 15, HW 16, Page 255
|
|
Interrupts: 160328
|
|
BIOS Control Word: 0x18b6
|
|
Adapter Control Word: 0x005b
|
|
Extended Translation: Enabled
|
|
Disconnect Enable Flags: 0xffff
|
|
Ultra Enable Flags: 0x0001
|
|
Tag Queue Enable Flags: 0x0000
|
|
Ordered Queue Tag Flags: 0x0000
|
|
Default Tag Queue Depth: 8
|
|
Tagged Queue By Device array for aic7xxx host instance 0:
|
|
{255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
|
|
Actual queue depth per device for aic7xxx host instance 0:
|
|
{1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
|
|
Statistics:
|
|
(scsi0:0:0:0)
|
|
Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
|
|
Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
|
|
Total transfers 160151 (74577 reads and 85574 writes)
|
|
(scsi0:0:6:0)
|
|
Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
|
|
Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
|
|
Total transfers 0 (0 reads and 0 writes)
|
|
|
|
|
|
1.6 Parallel port info in /proc/parport
|
|
---------------------------------------
|
|
|
|
The directory /proc/parport contains information about the parallel ports of
|
|
your system. It has one subdirectory for each port, named after the port
|
|
number (0,1,2,...).
|
|
|
|
These directories contain the four files shown in Table 1-8.
|
|
|
|
|
|
Table 1-8: Files in /proc/parport
|
|
..............................................................................
|
|
File Content
|
|
autoprobe Any IEEE-1284 device ID information that has been acquired.
|
|
devices list of the device drivers using that port. A + will appear by the
|
|
name of the device currently using the port (it might not appear
|
|
against any).
|
|
hardware Parallel port's base address, IRQ line and DMA channel.
|
|
irq IRQ that parport is using for that port. This is in a separate
|
|
file to allow you to alter it by writing a new value in (IRQ
|
|
number or none).
|
|
..............................................................................
|
|
|
|
1.7 TTY info in /proc/tty
|
|
-------------------------
|
|
|
|
Information about the available and actually used tty's can be found in the
|
|
directory /proc/tty.You'll find entries for drivers and line disciplines in
|
|
this directory, as shown in Table 1-9.
|
|
|
|
|
|
Table 1-9: Files in /proc/tty
|
|
..............................................................................
|
|
File Content
|
|
drivers list of drivers and their usage
|
|
ldiscs registered line disciplines
|
|
driver/serial usage statistic and status of single tty lines
|
|
..............................................................................
|
|
|
|
To see which tty's are currently in use, you can simply look into the file
|
|
/proc/tty/drivers:
|
|
|
|
> cat /proc/tty/drivers
|
|
pty_slave /dev/pts 136 0-255 pty:slave
|
|
pty_master /dev/ptm 128 0-255 pty:master
|
|
pty_slave /dev/ttyp 3 0-255 pty:slave
|
|
pty_master /dev/pty 2 0-255 pty:master
|
|
serial /dev/cua 5 64-67 serial:callout
|
|
serial /dev/ttyS 4 64-67 serial
|
|
/dev/tty0 /dev/tty0 4 0 system:vtmaster
|
|
/dev/ptmx /dev/ptmx 5 2 system
|
|
/dev/console /dev/console 5 1 system:console
|
|
/dev/tty /dev/tty 5 0 system:/dev/tty
|
|
unknown /dev/tty 4 1-63 console
|
|
|
|
|
|
1.8 Miscellaneous kernel statistics in /proc/stat
|
|
-------------------------------------------------
|
|
|
|
Various pieces of information about kernel activity are available in the
|
|
/proc/stat file. All of the numbers reported in this file are aggregates
|
|
since the system first booted. For a quick look, simply cat the file:
|
|
|
|
> cat /proc/stat
|
|
cpu 2255 34 2290 22625563 6290 127 456 0
|
|
cpu0 1132 34 1441 11311718 3675 127 438 0
|
|
cpu1 1123 0 849 11313845 2614 0 18 0
|
|
intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
|
|
ctxt 1990473
|
|
btime 1062191376
|
|
processes 2915
|
|
procs_running 1
|
|
procs_blocked 0
|
|
|
|
The very first "cpu" line aggregates the numbers in all of the other "cpuN"
|
|
lines. These numbers identify the amount of time the CPU has spent performing
|
|
different kinds of work. Time units are in USER_HZ (typically hundredths of a
|
|
second). The meanings of the columns are as follows, from left to right:
|
|
|
|
- user: normal processes executing in user mode
|
|
- nice: niced processes executing in user mode
|
|
- system: processes executing in kernel mode
|
|
- idle: twiddling thumbs
|
|
- iowait: waiting for I/O to complete
|
|
- irq: servicing interrupts
|
|
- softirq: servicing softirqs
|
|
- steal: involuntary wait
|
|
|
|
The "intr" line gives counts of interrupts serviced since boot time, for each
|
|
of the possible system interrupts. The first column is the total of all
|
|
interrupts serviced; each subsequent column is the total for that particular
|
|
interrupt.
|
|
|
|
The "ctxt" line gives the total number of context switches across all CPUs.
|
|
|
|
The "btime" line gives the time at which the system booted, in seconds since
|
|
the Unix epoch.
|
|
|
|
The "processes" line gives the number of processes and threads created, which
|
|
includes (but is not limited to) those created by calls to the fork() and
|
|
clone() system calls.
|
|
|
|
The "procs_running" line gives the number of processes currently running on
|
|
CPUs.
|
|
|
|
The "procs_blocked" line gives the number of processes currently blocked,
|
|
waiting for I/O to complete.
|
|
|
|
1.9 Ext4 file system parameters
|
|
------------------------------
|
|
Ext4 file system have one directory per partition under /proc/fs/ext4/
|
|
# ls /proc/fs/ext4/hdc/
|
|
group_prealloc max_to_scan mb_groups mb_history min_to_scan order2_req
|
|
stats stream_req
|
|
|
|
mb_groups:
|
|
This file gives the details of mutiblock allocator buddy cache of free blocks
|
|
|
|
mb_history:
|
|
Multiblock allocation history.
|
|
|
|
stats:
|
|
This file indicate whether the multiblock allocator should start collecting
|
|
statistics. The statistics are shown during unmount
|
|
|
|
group_prealloc:
|
|
The multiblock allocator normalize the block allocation request to
|
|
group_prealloc filesystem blocks if we don't have strip value set.
|
|
The stripe value can be specified at mount time or during mke2fs.
|
|
|
|
max_to_scan:
|
|
How long multiblock allocator can look for a best extent (in found extents)
|
|
|
|
min_to_scan:
|
|
How long multiblock allocator must look for a best extent
|
|
|
|
order2_req:
|
|
Multiblock allocator use 2^N search using buddies only for requests greater
|
|
than or equal to order2_req. The request size is specfied in file system
|
|
blocks. A value of 2 indicate only if the requests are greater than or equal
|
|
to 4 blocks.
|
|
|
|
stream_req:
|
|
Files smaller than stream_req are served by the stream allocator, whose
|
|
purpose is to pack requests as close each to other as possible to
|
|
produce smooth I/O traffic. Avalue of 16 indicate that file smaller than 16
|
|
filesystem block size will use group based preallocation.
|
|
|
|
------------------------------------------------------------------------------
|
|
Summary
|
|
------------------------------------------------------------------------------
|
|
The /proc file system serves information about the running system. It not only
|
|
allows access to process data but also allows you to request the kernel status
|
|
by reading files in the hierarchy.
|
|
|
|
The directory structure of /proc reflects the types of information and makes
|
|
it easy, if not obvious, where to look for specific data.
|
|
------------------------------------------------------------------------------
|
|
|
|
------------------------------------------------------------------------------
|
|
CHAPTER 2: MODIFYING SYSTEM PARAMETERS
|
|
------------------------------------------------------------------------------
|
|
|
|
------------------------------------------------------------------------------
|
|
In This Chapter
|
|
------------------------------------------------------------------------------
|
|
* Modifying kernel parameters by writing into files found in /proc/sys
|
|
* Exploring the files which modify certain parameters
|
|
* Review of the /proc/sys file tree
|
|
------------------------------------------------------------------------------
|
|
|
|
|
|
A very interesting part of /proc is the directory /proc/sys. This is not only
|
|
a source of information, it also allows you to change parameters within the
|
|
kernel. Be very careful when attempting this. You can optimize your system,
|
|
but you can also cause it to crash. Never alter kernel parameters on a
|
|
production system. Set up a development machine and test to make sure that
|
|
everything works the way you want it to. You may have no alternative but to
|
|
reboot the machine once an error has been made.
|
|
|
|
To change a value, simply echo the new value into the file. An example is
|
|
given below in the section on the file system data. You need to be root to do
|
|
this. You can create your own boot script to perform this every time your
|
|
system boots.
|
|
|
|
The files in /proc/sys can be used to fine tune and monitor miscellaneous and
|
|
general things in the operation of the Linux kernel. Since some of the files
|
|
can inadvertently disrupt your system, it is advisable to read both
|
|
documentation and source before actually making adjustments. In any case, be
|
|
very careful when writing to any of these files. The entries in /proc may
|
|
change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
|
|
review the kernel documentation in the directory /usr/src/linux/Documentation.
|
|
This chapter is heavily based on the documentation included in the pre 2.2
|
|
kernels, and became part of it in version 2.2.1 of the Linux kernel.
|
|
|
|
2.1 /proc/sys/fs - File system data
|
|
-----------------------------------
|
|
|
|
This subdirectory contains specific file system, file handle, inode, dentry
|
|
and quota information.
|
|
|
|
Currently, these files are in /proc/sys/fs:
|
|
|
|
dentry-state
|
|
------------
|
|
|
|
Status of the directory cache. Since directory entries are dynamically
|
|
allocated and deallocated, this file indicates the current status. It holds
|
|
six values, in which the last two are not used and are always zero. The others
|
|
are listed in table 2-1.
|
|
|
|
|
|
Table 2-1: Status files of the directory cache
|
|
..............................................................................
|
|
File Content
|
|
nr_dentry Almost always zero
|
|
nr_unused Number of unused cache entries
|
|
age_limit
|
|
in seconds after the entry may be reclaimed, when memory is short
|
|
want_pages internally
|
|
..............................................................................
|
|
|
|
dquot-nr and dquot-max
|
|
----------------------
|
|
|
|
The file dquot-max shows the maximum number of cached disk quota entries.
|
|
|
|
The file dquot-nr shows the number of allocated disk quota entries and the
|
|
number of free disk quota entries.
|
|
|
|
If the number of available cached disk quotas is very low and you have a large
|
|
number of simultaneous system users, you might want to raise the limit.
|
|
|
|
file-nr and file-max
|
|
--------------------
|
|
|
|
The kernel allocates file handles dynamically, but doesn't free them again at
|
|
this time.
|
|
|
|
The value in file-max denotes the maximum number of file handles that the
|
|
Linux kernel will allocate. When you get a lot of error messages about running
|
|
out of file handles, you might want to raise this limit. The default value is
|
|
10% of RAM in kilobytes. To change it, just write the new number into the
|
|
file:
|
|
|
|
# cat /proc/sys/fs/file-max
|
|
4096
|
|
# echo 8192 > /proc/sys/fs/file-max
|
|
# cat /proc/sys/fs/file-max
|
|
8192
|
|
|
|
|
|
This method of revision is useful for all customizable parameters of the
|
|
kernel - simply echo the new value to the corresponding file.
|
|
|
|
Historically, the three values in file-nr denoted the number of allocated file
|
|
handles, the number of allocated but unused file handles, and the maximum
|
|
number of file handles. Linux 2.6 always reports 0 as the number of free file
|
|
handles -- this is not an error, it just means that the number of allocated
|
|
file handles exactly matches the number of used file handles.
|
|
|
|
Attempts to allocate more file descriptors than file-max are reported with
|
|
printk, look for "VFS: file-max limit <number> reached".
|
|
|
|
inode-state and inode-nr
|
|
------------------------
|
|
|
|
The file inode-nr contains the first two items from inode-state, so we'll skip
|
|
to that file...
|
|
|
|
inode-state contains two actual numbers and five dummy values. The numbers
|
|
are nr_inodes and nr_free_inodes (in order of appearance).
|
|
|
|
nr_inodes
|
|
~~~~~~~~~
|
|
|
|
Denotes the number of inodes the system has allocated. This number will
|
|
grow and shrink dynamically.
|
|
|
|
nr_open
|
|
-------
|
|
|
|
Denotes the maximum number of file-handles a process can
|
|
allocate. Default value is 1024*1024 (1048576) which should be
|
|
enough for most machines. Actual limit depends on RLIMIT_NOFILE
|
|
resource limit.
|
|
|
|
nr_free_inodes
|
|
--------------
|
|
|
|
Represents the number of free inodes. Ie. The number of inuse inodes is
|
|
(nr_inodes - nr_free_inodes).
|
|
|
|
aio-nr and aio-max-nr
|
|
---------------------
|
|
|
|
aio-nr is the running total of the number of events specified on the
|
|
io_setup system call for all currently active aio contexts. If aio-nr
|
|
reaches aio-max-nr then io_setup will fail with EAGAIN. Note that
|
|
raising aio-max-nr does not result in the pre-allocation or re-sizing
|
|
of any kernel data structures.
|
|
|
|
2.2 /proc/sys/fs/binfmt_misc - Miscellaneous binary formats
|
|
-----------------------------------------------------------
|
|
|
|
Besides these files, there is the subdirectory /proc/sys/fs/binfmt_misc. This
|
|
handles the kernel support for miscellaneous binary formats.
|
|
|
|
Binfmt_misc provides the ability to register additional binary formats to the
|
|
Kernel without compiling an additional module/kernel. Therefore, binfmt_misc
|
|
needs to know magic numbers at the beginning or the filename extension of the
|
|
binary.
|
|
|
|
It works by maintaining a linked list of structs that contain a description of
|
|
a binary format, including a magic with size (or the filename extension),
|
|
offset and mask, and the interpreter name. On request it invokes the given
|
|
interpreter with the original program as argument, as binfmt_java and
|
|
binfmt_em86 and binfmt_mz do. Since binfmt_misc does not define any default
|
|
binary-formats, you have to register an additional binary-format.
|
|
|
|
There are two general files in binfmt_misc and one file per registered format.
|
|
The two general files are register and status.
|
|
|
|
Registering a new binary format
|
|
-------------------------------
|
|
|
|
To register a new binary format you have to issue the command
|
|
|
|
echo :name:type:offset:magic:mask:interpreter: > /proc/sys/fs/binfmt_misc/register
|
|
|
|
|
|
|
|
with appropriate name (the name for the /proc-dir entry), offset (defaults to
|
|
0, if omitted), magic, mask (which can be omitted, defaults to all 0xff) and
|
|
last but not least, the interpreter that is to be invoked (for example and
|
|
testing /bin/echo). Type can be M for usual magic matching or E for filename
|
|
extension matching (give extension in place of magic).
|
|
|
|
Check or reset the status of the binary format handler
|
|
------------------------------------------------------
|
|
|
|
If you do a cat on the file /proc/sys/fs/binfmt_misc/status, you will get the
|
|
current status (enabled/disabled) of binfmt_misc. Change the status by echoing
|
|
0 (disables) or 1 (enables) or -1 (caution: this clears all previously
|
|
registered binary formats) to status. For example echo 0 > status to disable
|
|
binfmt_misc (temporarily).
|
|
|
|
Status of a single handler
|
|
--------------------------
|
|
|
|
Each registered handler has an entry in /proc/sys/fs/binfmt_misc. These files
|
|
perform the same function as status, but their scope is limited to the actual
|
|
binary format. By cating this file, you also receive all related information
|
|
about the interpreter/magic of the binfmt.
|
|
|
|
Example usage of binfmt_misc (emulate binfmt_java)
|
|
--------------------------------------------------
|
|
|
|
cd /proc/sys/fs/binfmt_misc
|
|
echo ':Java:M::\xca\xfe\xba\xbe::/usr/local/java/bin/javawrapper:' > register
|
|
echo ':HTML:E::html::/usr/local/java/bin/appletviewer:' > register
|
|
echo ':Applet:M::<!--applet::/usr/local/java/bin/appletviewer:' > register
|
|
echo ':DEXE:M::\x0eDEX::/usr/bin/dosexec:' > register
|
|
|
|
|
|
These four lines add support for Java executables and Java applets (like
|
|
binfmt_java, additionally recognizing the .html extension with no need to put
|
|
<!--applet> to every applet file). You have to install the JDK and the
|
|
shell-script /usr/local/java/bin/javawrapper too. It works around the
|
|
brokenness of the Java filename handling. To add a Java binary, just create a
|
|
link to the class-file somewhere in the path.
|
|
|
|
2.3 /proc/sys/kernel - general kernel parameters
|
|
------------------------------------------------
|
|
|
|
This directory reflects general kernel behaviors. As I've said before, the
|
|
contents depend on your configuration. Here you'll find the most important
|
|
files, along with descriptions of what they mean and how to use them.
|
|
|
|
acct
|
|
----
|
|
|
|
The file contains three values; highwater, lowwater, and frequency.
|
|
|
|
It exists only when BSD-style process accounting is enabled. These values
|
|
control its behavior. If the free space on the file system where the log lives
|
|
goes below lowwater percentage, accounting suspends. If it goes above
|
|
highwater percentage, accounting resumes. Frequency determines how often you
|
|
check the amount of free space (value is in seconds). Default settings are: 4,
|
|
2, and 30. That is, suspend accounting if there is less than 2 percent free;
|
|
resume it if we have a value of 3 or more percent; consider information about
|
|
the amount of free space valid for 30 seconds
|
|
|
|
ctrl-alt-del
|
|
------------
|
|
|
|
When the value in this file is 0, ctrl-alt-del is trapped and sent to the init
|
|
program to handle a graceful restart. However, when the value is greater that
|
|
zero, Linux's reaction to this key combination will be an immediate reboot,
|
|
without syncing its dirty buffers.
|
|
|
|
[NOTE]
|
|
When a program (like dosemu) has the keyboard in raw mode, the
|
|
ctrl-alt-del is intercepted by the program before it ever reaches the
|
|
kernel tty layer, and it is up to the program to decide what to do with
|
|
it.
|
|
|
|
domainname and hostname
|
|
-----------------------
|
|
|
|
These files can be controlled to set the NIS domainname and hostname of your
|
|
box. For the classic darkstar.frop.org a simple:
|
|
|
|
# echo "darkstar" > /proc/sys/kernel/hostname
|
|
# echo "frop.org" > /proc/sys/kernel/domainname
|
|
|
|
|
|
would suffice to set your hostname and NIS domainname.
|
|
|
|
osrelease, ostype and version
|
|
-----------------------------
|
|
|
|
The names make it pretty obvious what these fields contain:
|
|
|
|
> cat /proc/sys/kernel/osrelease
|
|
2.2.12
|
|
|
|
> cat /proc/sys/kernel/ostype
|
|
Linux
|
|
|
|
> cat /proc/sys/kernel/version
|
|
#4 Fri Oct 1 12:41:14 PDT 1999
|
|
|
|
|
|
The files osrelease and ostype should be clear enough. Version needs a little
|
|
more clarification. The #4 means that this is the 4th kernel built from this
|
|
source base and the date after it indicates the time the kernel was built. The
|
|
only way to tune these values is to rebuild the kernel.
|
|
|
|
panic
|
|
-----
|
|
|
|
The value in this file represents the number of seconds the kernel waits
|
|
before rebooting on a panic. When you use the software watchdog, the
|
|
recommended setting is 60. If set to 0, the auto reboot after a kernel panic
|
|
is disabled, which is the default setting.
|
|
|
|
printk
|
|
------
|
|
|
|
The four values in printk denote
|
|
* console_loglevel,
|
|
* default_message_loglevel,
|
|
* minimum_console_loglevel and
|
|
* default_console_loglevel
|
|
respectively.
|
|
|
|
These values influence printk() behavior when printing or logging error
|
|
messages, which come from inside the kernel. See syslog(2) for more
|
|
information on the different log levels.
|
|
|
|
console_loglevel
|
|
----------------
|
|
|
|
Messages with a higher priority than this will be printed to the console.
|
|
|
|
default_message_level
|
|
---------------------
|
|
|
|
Messages without an explicit priority will be printed with this priority.
|
|
|
|
minimum_console_loglevel
|
|
------------------------
|
|
|
|
Minimum (highest) value to which the console_loglevel can be set.
|
|
|
|
default_console_loglevel
|
|
------------------------
|
|
|
|
Default value for console_loglevel.
|
|
|
|
sg-big-buff
|
|
-----------
|
|
|
|
This file shows the size of the generic SCSI (sg) buffer. At this point, you
|
|
can't tune it yet, but you can change it at compile time by editing
|
|
include/scsi/sg.h and changing the value of SG_BIG_BUFF.
|
|
|
|
If you use a scanner with SANE (Scanner Access Now Easy) you might want to set
|
|
this to a higher value. Refer to the SANE documentation on this issue.
|
|
|
|
modprobe
|
|
--------
|
|
|
|
The location where the modprobe binary is located. The kernel uses this
|
|
program to load modules on demand.
|
|
|
|
unknown_nmi_panic
|
|
-----------------
|
|
|
|
The value in this file affects behavior of handling NMI. When the value is
|
|
non-zero, unknown NMI is trapped and then panic occurs. At that time, kernel
|
|
debugging information is displayed on console.
|
|
|
|
NMI switch that most IA32 servers have fires unknown NMI up, for example.
|
|
If a system hangs up, try pressing the NMI switch.
|
|
|
|
nmi_watchdog
|
|
------------
|
|
|
|
Enables/Disables the NMI watchdog on x86 systems. When the value is non-zero
|
|
the NMI watchdog is enabled and will continuously test all online cpus to
|
|
determine whether or not they are still functioning properly.
|
|
|
|
Because the NMI watchdog shares registers with oprofile, by disabling the NMI
|
|
watchdog, oprofile may have more registers to utilize.
|
|
|
|
maps_protect
|
|
------------
|
|
|
|
Enables/Disables the protection of the per-process proc entries "maps" and
|
|
"smaps". When enabled, the contents of these files are visible only to
|
|
readers that are allowed to ptrace() the given process.
|
|
|
|
|
|
2.4 /proc/sys/vm - The virtual memory subsystem
|
|
-----------------------------------------------
|
|
|
|
The files in this directory can be used to tune the operation of the virtual
|
|
memory (VM) subsystem of the Linux kernel.
|
|
|
|
vfs_cache_pressure
|
|
------------------
|
|
|
|
Controls the tendency of the kernel to reclaim the memory which is used for
|
|
caching of directory and inode objects.
|
|
|
|
At the default value of vfs_cache_pressure=100 the kernel will attempt to
|
|
reclaim dentries and inodes at a "fair" rate with respect to pagecache and
|
|
swapcache reclaim. Decreasing vfs_cache_pressure causes the kernel to prefer
|
|
to retain dentry and inode caches. Increasing vfs_cache_pressure beyond 100
|
|
causes the kernel to prefer to reclaim dentries and inodes.
|
|
|
|
dirty_background_ratio
|
|
----------------------
|
|
|
|
Contains, as a percentage of total system memory, the number of pages at which
|
|
the pdflush background writeback daemon will start writing out dirty data.
|
|
|
|
dirty_ratio
|
|
-----------------
|
|
|
|
Contains, as a percentage of total system memory, the number of pages at which
|
|
a process which is generating disk writes will itself start writing out dirty
|
|
data.
|
|
|
|
dirty_writeback_centisecs
|
|
-------------------------
|
|
|
|
The pdflush writeback daemons will periodically wake up and write `old' data
|
|
out to disk. This tunable expresses the interval between those wakeups, in
|
|
100'ths of a second.
|
|
|
|
Setting this to zero disables periodic writeback altogether.
|
|
|
|
dirty_expire_centisecs
|
|
----------------------
|
|
|
|
This tunable is used to define when dirty data is old enough to be eligible
|
|
for writeout by the pdflush daemons. It is expressed in 100'ths of a second.
|
|
Data which has been dirty in-memory for longer than this interval will be
|
|
written out next time a pdflush daemon wakes up.
|
|
|
|
highmem_is_dirtyable
|
|
--------------------
|
|
|
|
Only present if CONFIG_HIGHMEM is set.
|
|
|
|
This defaults to 0 (false), meaning that the ratios set above are calculated
|
|
as a percentage of lowmem only. This protects against excessive scanning
|
|
in page reclaim, swapping and general VM distress.
|
|
|
|
Setting this to 1 can be useful on 32 bit machines where you want to make
|
|
random changes within an MMAPed file that is larger than your available
|
|
lowmem without causing large quantities of random IO. Is is safe if the
|
|
behavior of all programs running on the machine is known and memory will
|
|
not be otherwise stressed.
|
|
|
|
legacy_va_layout
|
|
----------------
|
|
|
|
If non-zero, this sysctl disables the new 32-bit mmap mmap layout - the kernel
|
|
will use the legacy (2.4) layout for all processes.
|
|
|
|
lowmem_reserve_ratio
|
|
---------------------
|
|
|
|
For some specialised workloads on highmem machines it is dangerous for
|
|
the kernel to allow process memory to be allocated from the "lowmem"
|
|
zone. This is because that memory could then be pinned via the mlock()
|
|
system call, or by unavailability of swapspace.
|
|
|
|
And on large highmem machines this lack of reclaimable lowmem memory
|
|
can be fatal.
|
|
|
|
So the Linux page allocator has a mechanism which prevents allocations
|
|
which _could_ use highmem from using too much lowmem. This means that
|
|
a certain amount of lowmem is defended from the possibility of being
|
|
captured into pinned user memory.
|
|
|
|
(The same argument applies to the old 16 megabyte ISA DMA region. This
|
|
mechanism will also defend that region from allocations which could use
|
|
highmem or lowmem).
|
|
|
|
The `lowmem_reserve_ratio' tunable determines how aggressive the kernel is
|
|
in defending these lower zones.
|
|
|
|
If you have a machine which uses highmem or ISA DMA and your
|
|
applications are using mlock(), or if you are running with no swap then
|
|
you probably should change the lowmem_reserve_ratio setting.
|
|
|
|
The lowmem_reserve_ratio is an array. You can see them by reading this file.
|
|
-
|
|
% cat /proc/sys/vm/lowmem_reserve_ratio
|
|
256 256 32
|
|
-
|
|
Note: # of this elements is one fewer than number of zones. Because the highest
|
|
zone's value is not necessary for following calculation.
|
|
|
|
But, these values are not used directly. The kernel calculates # of protection
|
|
pages for each zones from them. These are shown as array of protection pages
|
|
in /proc/zoneinfo like followings. (This is an example of x86-64 box).
|
|
Each zone has an array of protection pages like this.
|
|
|
|
-
|
|
Node 0, zone DMA
|
|
pages free 1355
|
|
min 3
|
|
low 3
|
|
high 4
|
|
:
|
|
:
|
|
numa_other 0
|
|
protection: (0, 2004, 2004, 2004)
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
pagesets
|
|
cpu: 0 pcp: 0
|
|
:
|
|
-
|
|
These protections are added to score to judge whether this zone should be used
|
|
for page allocation or should be reclaimed.
|
|
|
|
In this example, if normal pages (index=2) are required to this DMA zone and
|
|
pages_high is used for watermark, the kernel judges this zone should not be
|
|
used because pages_free(1355) is smaller than watermark + protection[2]
|
|
(4 + 2004 = 2008). If this protection value is 0, this zone would be used for
|
|
normal page requirement. If requirement is DMA zone(index=0), protection[0]
|
|
(=0) is used.
|
|
|
|
zone[i]'s protection[j] is calculated by following exprssion.
|
|
|
|
(i < j):
|
|
zone[i]->protection[j]
|
|
= (total sums of present_pages from zone[i+1] to zone[j] on the node)
|
|
/ lowmem_reserve_ratio[i];
|
|
(i = j):
|
|
(should not be protected. = 0;
|
|
(i > j):
|
|
(not necessary, but looks 0)
|
|
|
|
The default values of lowmem_reserve_ratio[i] are
|
|
256 (if zone[i] means DMA or DMA32 zone)
|
|
32 (others).
|
|
As above expression, they are reciprocal number of ratio.
|
|
256 means 1/256. # of protection pages becomes about "0.39%" of total present
|
|
pages of higher zones on the node.
|
|
|
|
If you would like to protect more pages, smaller values are effective.
|
|
The minimum value is 1 (1/1 -> 100%).
|
|
|
|
page-cluster
|
|
------------
|
|
|
|
page-cluster controls the number of pages which are written to swap in
|
|
a single attempt. The swap I/O size.
|
|
|
|
It is a logarithmic value - setting it to zero means "1 page", setting
|
|
it to 1 means "2 pages", setting it to 2 means "4 pages", etc.
|
|
|
|
The default value is three (eight pages at a time). There may be some
|
|
small benefits in tuning this to a different value if your workload is
|
|
swap-intensive.
|
|
|
|
overcommit_memory
|
|
-----------------
|
|
|
|
Controls overcommit of system memory, possibly allowing processes
|
|
to allocate (but not use) more memory than is actually available.
|
|
|
|
|
|
0 - Heuristic overcommit handling. Obvious overcommits of
|
|
address space are refused. Used for a typical system. It
|
|
ensures a seriously wild allocation fails while allowing
|
|
overcommit to reduce swap usage. root is allowed to
|
|
allocate slightly more memory in this mode. This is the
|
|
default.
|
|
|
|
1 - Always overcommit. Appropriate for some scientific
|
|
applications.
|
|
|
|
2 - Don't overcommit. The total address space commit
|
|
for the system is not permitted to exceed swap plus a
|
|
configurable percentage (default is 50) of physical RAM.
|
|
Depending on the percentage you use, in most situations
|
|
this means a process will not be killed while attempting
|
|
to use already-allocated memory but will receive errors
|
|
on memory allocation as appropriate.
|
|
|
|
overcommit_ratio
|
|
----------------
|
|
|
|
Percentage of physical memory size to include in overcommit calculations
|
|
(see above.)
|
|
|
|
Memory allocation limit = swapspace + physmem * (overcommit_ratio / 100)
|
|
|
|
swapspace = total size of all swap areas
|
|
physmem = size of physical memory in system
|
|
|
|
nr_hugepages and hugetlb_shm_group
|
|
----------------------------------
|
|
|
|
nr_hugepages configures number of hugetlb page reserved for the system.
|
|
|
|
hugetlb_shm_group contains group id that is allowed to create SysV shared
|
|
memory segment using hugetlb page.
|
|
|
|
hugepages_treat_as_movable
|
|
--------------------------
|
|
|
|
This parameter is only useful when kernelcore= is specified at boot time to
|
|
create ZONE_MOVABLE for pages that may be reclaimed or migrated. Huge pages
|
|
are not movable so are not normally allocated from ZONE_MOVABLE. A non-zero
|
|
value written to hugepages_treat_as_movable allows huge pages to be allocated
|
|
from ZONE_MOVABLE.
|
|
|
|
Once enabled, the ZONE_MOVABLE is treated as an area of memory the huge
|
|
pages pool can easily grow or shrink within. Assuming that applications are
|
|
not running that mlock() a lot of memory, it is likely the huge pages pool
|
|
can grow to the size of ZONE_MOVABLE by repeatedly entering the desired value
|
|
into nr_hugepages and triggering page reclaim.
|
|
|
|
laptop_mode
|
|
-----------
|
|
|
|
laptop_mode is a knob that controls "laptop mode". All the things that are
|
|
controlled by this knob are discussed in Documentation/laptops/laptop-mode.txt.
|
|
|
|
block_dump
|
|
----------
|
|
|
|
block_dump enables block I/O debugging when set to a nonzero value. More
|
|
information on block I/O debugging is in Documentation/laptops/laptop-mode.txt.
|
|
|
|
swap_token_timeout
|
|
------------------
|
|
|
|
This file contains valid hold time of swap out protection token. The Linux
|
|
VM has token based thrashing control mechanism and uses the token to prevent
|
|
unnecessary page faults in thrashing situation. The unit of the value is
|
|
second. The value would be useful to tune thrashing behavior.
|
|
|
|
drop_caches
|
|
-----------
|
|
|
|
Writing to this will cause the kernel to drop clean caches, dentries and
|
|
inodes from memory, causing that memory to become free.
|
|
|
|
To free pagecache:
|
|
echo 1 > /proc/sys/vm/drop_caches
|
|
To free dentries and inodes:
|
|
echo 2 > /proc/sys/vm/drop_caches
|
|
To free pagecache, dentries and inodes:
|
|
echo 3 > /proc/sys/vm/drop_caches
|
|
|
|
As this is a non-destructive operation and dirty objects are not freeable, the
|
|
user should run `sync' first.
|
|
|
|
|
|
2.5 /proc/sys/dev - Device specific parameters
|
|
----------------------------------------------
|
|
|
|
Currently there is only support for CDROM drives, and for those, there is only
|
|
one read-only file containing information about the CD-ROM drives attached to
|
|
the system:
|
|
|
|
>cat /proc/sys/dev/cdrom/info
|
|
CD-ROM information, Id: cdrom.c 2.55 1999/04/25
|
|
|
|
drive name: sr0 hdb
|
|
drive speed: 32 40
|
|
drive # of slots: 1 0
|
|
Can close tray: 1 1
|
|
Can open tray: 1 1
|
|
Can lock tray: 1 1
|
|
Can change speed: 1 1
|
|
Can select disk: 0 1
|
|
Can read multisession: 1 1
|
|
Can read MCN: 1 1
|
|
Reports media changed: 1 1
|
|
Can play audio: 1 1
|
|
|
|
|
|
You see two drives, sr0 and hdb, along with a list of their features.
|
|
|
|
2.6 /proc/sys/sunrpc - Remote procedure calls
|
|
---------------------------------------------
|
|
|
|
This directory contains four files, which enable or disable debugging for the
|
|
RPC functions NFS, NFS-daemon, RPC and NLM. The default values are 0. They can
|
|
be set to one to turn debugging on. (The default value is 0 for each)
|
|
|
|
2.7 /proc/sys/net - Networking stuff
|
|
------------------------------------
|
|
|
|
The interface to the networking parts of the kernel is located in
|
|
/proc/sys/net. Table 2-3 shows all possible subdirectories. You may see only
|
|
some of them, depending on your kernel's configuration.
|
|
|
|
|
|
Table 2-3: Subdirectories in /proc/sys/net
|
|
..............................................................................
|
|
Directory Content Directory Content
|
|
core General parameter appletalk Appletalk protocol
|
|
unix Unix domain sockets netrom NET/ROM
|
|
802 E802 protocol ax25 AX25
|
|
ethernet Ethernet protocol rose X.25 PLP layer
|
|
ipv4 IP version 4 x25 X.25 protocol
|
|
ipx IPX token-ring IBM token ring
|
|
bridge Bridging decnet DEC net
|
|
ipv6 IP version 6
|
|
..............................................................................
|
|
|
|
We will concentrate on IP networking here. Since AX15, X.25, and DEC Net are
|
|
only minor players in the Linux world, we'll skip them in this chapter. You'll
|
|
find some short info on Appletalk and IPX further on in this chapter. Review
|
|
the online documentation and the kernel source to get a detailed view of the
|
|
parameters for those protocols. In this section we'll discuss the
|
|
subdirectories printed in bold letters in the table above. As default values
|
|
are suitable for most needs, there is no need to change these values.
|
|
|
|
/proc/sys/net/core - Network core options
|
|
-----------------------------------------
|
|
|
|
rmem_default
|
|
------------
|
|
|
|
The default setting of the socket receive buffer in bytes.
|
|
|
|
rmem_max
|
|
--------
|
|
|
|
The maximum receive socket buffer size in bytes.
|
|
|
|
wmem_default
|
|
------------
|
|
|
|
The default setting (in bytes) of the socket send buffer.
|
|
|
|
wmem_max
|
|
--------
|
|
|
|
The maximum send socket buffer size in bytes.
|
|
|
|
message_burst and message_cost
|
|
------------------------------
|
|
|
|
These parameters are used to limit the warning messages written to the kernel
|
|
log from the networking code. They enforce a rate limit to make a
|
|
denial-of-service attack impossible. A higher message_cost factor, results in
|
|
fewer messages that will be written. Message_burst controls when messages will
|
|
be dropped. The default settings limit warning messages to one every five
|
|
seconds.
|
|
|
|
warnings
|
|
--------
|
|
|
|
This controls console messages from the networking stack that can occur because
|
|
of problems on the network like duplicate address or bad checksums. Normally,
|
|
this should be enabled, but if the problem persists the messages can be
|
|
disabled.
|
|
|
|
|
|
netdev_max_backlog
|
|
------------------
|
|
|
|
Maximum number of packets, queued on the INPUT side, when the interface
|
|
receives packets faster than kernel can process them.
|
|
|
|
optmem_max
|
|
----------
|
|
|
|
Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
|
|
of struct cmsghdr structures with appended data.
|
|
|
|
/proc/sys/net/unix - Parameters for Unix domain sockets
|
|
-------------------------------------------------------
|
|
|
|
There are only two files in this subdirectory. They control the delays for
|
|
deleting and destroying socket descriptors.
|
|
|
|
2.8 /proc/sys/net/ipv4 - IPV4 settings
|
|
--------------------------------------
|
|
|
|
IP version 4 is still the most used protocol in Unix networking. It will be
|
|
replaced by IP version 6 in the next couple of years, but for the moment it's
|
|
the de facto standard for the internet and is used in most networking
|
|
environments around the world. Because of the importance of this protocol,
|
|
we'll have a deeper look into the subtree controlling the behavior of the IPv4
|
|
subsystem of the Linux kernel.
|
|
|
|
Let's start with the entries in /proc/sys/net/ipv4.
|
|
|
|
ICMP settings
|
|
-------------
|
|
|
|
icmp_echo_ignore_all and icmp_echo_ignore_broadcasts
|
|
----------------------------------------------------
|
|
|
|
Turn on (1) or off (0), if the kernel should ignore all ICMP ECHO requests, or
|
|
just those to broadcast and multicast addresses.
|
|
|
|
Please note that if you accept ICMP echo requests with a broadcast/multi\-cast
|
|
destination address your network may be used as an exploder for denial of
|
|
service packet flooding attacks to other hosts.
|
|
|
|
icmp_destunreach_rate, icmp_echoreply_rate, icmp_paramprob_rate and icmp_timeexeed_rate
|
|
---------------------------------------------------------------------------------------
|
|
|
|
Sets limits for sending ICMP packets to specific targets. A value of zero
|
|
disables all limiting. Any positive value sets the maximum package rate in
|
|
hundredth of a second (on Intel systems).
|
|
|
|
IP settings
|
|
-----------
|
|
|
|
ip_autoconfig
|
|
-------------
|
|
|
|
This file contains the number one if the host received its IP configuration by
|
|
RARP, BOOTP, DHCP or a similar mechanism. Otherwise it is zero.
|
|
|
|
ip_default_ttl
|
|
--------------
|
|
|
|
TTL (Time To Live) for IPv4 interfaces. This is simply the maximum number of
|
|
hops a packet may travel.
|
|
|
|
ip_dynaddr
|
|
----------
|
|
|
|
Enable dynamic socket address rewriting on interface address change. This is
|
|
useful for dialup interface with changing IP addresses.
|
|
|
|
ip_forward
|
|
----------
|
|
|
|
Enable or disable forwarding of IP packages between interfaces. Changing this
|
|
value resets all other parameters to their default values. They differ if the
|
|
kernel is configured as host or router.
|
|
|
|
ip_local_port_range
|
|
-------------------
|
|
|
|
Range of ports used by TCP and UDP to choose the local port. Contains two
|
|
numbers, the first number is the lowest port, the second number the highest
|
|
local port. Default is 1024-4999. Should be changed to 32768-61000 for
|
|
high-usage systems.
|
|
|
|
ip_no_pmtu_disc
|
|
---------------
|
|
|
|
Global switch to turn path MTU discovery off. It can also be set on a per
|
|
socket basis by the applications or on a per route basis.
|
|
|
|
ip_masq_debug
|
|
-------------
|
|
|
|
Enable/disable debugging of IP masquerading.
|
|
|
|
IP fragmentation settings
|
|
-------------------------
|
|
|
|
ipfrag_high_trash and ipfrag_low_trash
|
|
--------------------------------------
|
|
|
|
Maximum memory used to reassemble IP fragments. When ipfrag_high_thresh bytes
|
|
of memory is allocated for this purpose, the fragment handler will toss
|
|
packets until ipfrag_low_thresh is reached.
|
|
|
|
ipfrag_time
|
|
-----------
|
|
|
|
Time in seconds to keep an IP fragment in memory.
|
|
|
|
TCP settings
|
|
------------
|
|
|
|
tcp_ecn
|
|
-------
|
|
|
|
This file controls the use of the ECN bit in the IPv4 headers. This is a new
|
|
feature about Explicit Congestion Notification, but some routers and firewalls
|
|
block traffic that has this bit set, so it could be necessary to echo 0 to
|
|
/proc/sys/net/ipv4/tcp_ecn if you want to talk to these sites. For more info
|
|
you could read RFC2481.
|
|
|
|
tcp_retrans_collapse
|
|
--------------------
|
|
|
|
Bug-to-bug compatibility with some broken printers. On retransmit, try to send
|
|
larger packets to work around bugs in certain TCP stacks. Can be turned off by
|
|
setting it to zero.
|
|
|
|
tcp_keepalive_probes
|
|
--------------------
|
|
|
|
Number of keep alive probes TCP sends out, until it decides that the
|
|
connection is broken.
|
|
|
|
tcp_keepalive_time
|
|
------------------
|
|
|
|
How often TCP sends out keep alive messages, when keep alive is enabled. The
|
|
default is 2 hours.
|
|
|
|
tcp_syn_retries
|
|
---------------
|
|
|
|
Number of times initial SYNs for a TCP connection attempt will be
|
|
retransmitted. Should not be higher than 255. This is only the timeout for
|
|
outgoing connections, for incoming connections the number of retransmits is
|
|
defined by tcp_retries1.
|
|
|
|
tcp_sack
|
|
--------
|
|
|
|
Enable select acknowledgments after RFC2018.
|
|
|
|
tcp_timestamps
|
|
--------------
|
|
|
|
Enable timestamps as defined in RFC1323.
|
|
|
|
tcp_stdurg
|
|
----------
|
|
|
|
Enable the strict RFC793 interpretation of the TCP urgent pointer field. The
|
|
default is to use the BSD compatible interpretation of the urgent pointer
|
|
pointing to the first byte after the urgent data. The RFC793 interpretation is
|
|
to have it point to the last byte of urgent data. Enabling this option may
|
|
lead to interoperability problems. Disabled by default.
|
|
|
|
tcp_syncookies
|
|
--------------
|
|
|
|
Only valid when the kernel was compiled with CONFIG_SYNCOOKIES. Send out
|
|
syncookies when the syn backlog queue of a socket overflows. This is to ward
|
|
off the common 'syn flood attack'. Disabled by default.
|
|
|
|
Note that the concept of a socket backlog is abandoned. This means the peer
|
|
may not receive reliable error messages from an over loaded server with
|
|
syncookies enabled.
|
|
|
|
tcp_window_scaling
|
|
------------------
|
|
|
|
Enable window scaling as defined in RFC1323.
|
|
|
|
tcp_fin_timeout
|
|
---------------
|
|
|
|
The length of time in seconds it takes to receive a final FIN before the
|
|
socket is always closed. This is strictly a violation of the TCP
|
|
specification, but required to prevent denial-of-service attacks.
|
|
|
|
tcp_max_ka_probes
|
|
-----------------
|
|
|
|
Indicates how many keep alive probes are sent per slow timer run. Should not
|
|
be set too high to prevent bursts.
|
|
|
|
tcp_max_syn_backlog
|
|
-------------------
|
|
|
|
Length of the per socket backlog queue. Since Linux 2.2 the backlog specified
|
|
in listen(2) only specifies the length of the backlog queue of already
|
|
established sockets. When more connection requests arrive Linux starts to drop
|
|
packets. When syncookies are enabled the packets are still answered and the
|
|
maximum queue is effectively ignored.
|
|
|
|
tcp_retries1
|
|
------------
|
|
|
|
Defines how often an answer to a TCP connection request is retransmitted
|
|
before giving up.
|
|
|
|
tcp_retries2
|
|
------------
|
|
|
|
Defines how often a TCP packet is retransmitted before giving up.
|
|
|
|
Interface specific settings
|
|
---------------------------
|
|
|
|
In the directory /proc/sys/net/ipv4/conf you'll find one subdirectory for each
|
|
interface the system knows about and one directory calls all. Changes in the
|
|
all subdirectory affect all interfaces, whereas changes in the other
|
|
subdirectories affect only one interface. All directories have the same
|
|
entries:
|
|
|
|
accept_redirects
|
|
----------------
|
|
|
|
This switch decides if the kernel accepts ICMP redirect messages or not. The
|
|
default is 'yes' if the kernel is configured for a regular host and 'no' for a
|
|
router configuration.
|
|
|
|
accept_source_route
|
|
-------------------
|
|
|
|
Should source routed packages be accepted or declined. The default is
|
|
dependent on the kernel configuration. It's 'yes' for routers and 'no' for
|
|
hosts.
|
|
|
|
bootp_relay
|
|
~~~~~~~~~~~
|
|
|
|
Accept packets with source address 0.b.c.d with destinations not to this host
|
|
as local ones. It is supposed that a BOOTP relay daemon will catch and forward
|
|
such packets.
|
|
|
|
The default is 0, since this feature is not implemented yet (kernel version
|
|
2.2.12).
|
|
|
|
forwarding
|
|
----------
|
|
|
|
Enable or disable IP forwarding on this interface.
|
|
|
|
log_martians
|
|
------------
|
|
|
|
Log packets with source addresses with no known route to kernel log.
|
|
|
|
mc_forwarding
|
|
-------------
|
|
|
|
Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE and a
|
|
multicast routing daemon is required.
|
|
|
|
proxy_arp
|
|
---------
|
|
|
|
Does (1) or does not (0) perform proxy ARP.
|
|
|
|
rp_filter
|
|
---------
|
|
|
|
Integer value determines if a source validation should be made. 1 means yes, 0
|
|
means no. Disabled by default, but local/broadcast address spoofing is always
|
|
on.
|
|
|
|
If you set this to 1 on a router that is the only connection for a network to
|
|
the net, it will prevent spoofing attacks against your internal networks
|
|
(external addresses can still be spoofed), without the need for additional
|
|
firewall rules.
|
|
|
|
secure_redirects
|
|
----------------
|
|
|
|
Accept ICMP redirect messages only for gateways, listed in default gateway
|
|
list. Enabled by default.
|
|
|
|
shared_media
|
|
------------
|
|
|
|
If it is not set the kernel does not assume that different subnets on this
|
|
device can communicate directly. Default setting is 'yes'.
|
|
|
|
send_redirects
|
|
--------------
|
|
|
|
Determines whether to send ICMP redirects to other hosts.
|
|
|
|
Routing settings
|
|
----------------
|
|
|
|
The directory /proc/sys/net/ipv4/route contains several file to control
|
|
routing issues.
|
|
|
|
error_burst and error_cost
|
|
--------------------------
|
|
|
|
These parameters are used to limit how many ICMP destination unreachable to
|
|
send from the host in question. ICMP destination unreachable messages are
|
|
sent when we cannot reach the next hop while trying to transmit a packet.
|
|
It will also print some error messages to kernel logs if someone is ignoring
|
|
our ICMP redirects. The higher the error_cost factor is, the fewer
|
|
destination unreachable and error messages will be let through. Error_burst
|
|
controls when destination unreachable messages and error messages will be
|
|
dropped. The default settings limit warning messages to five every second.
|
|
|
|
flush
|
|
-----
|
|
|
|
Writing to this file results in a flush of the routing cache.
|
|
|
|
gc_elasticity, gc_interval, gc_min_interval_ms, gc_timeout, gc_thresh
|
|
---------------------------------------------------------------------
|
|
|
|
Values to control the frequency and behavior of the garbage collection
|
|
algorithm for the routing cache. gc_min_interval is deprecated and replaced
|
|
by gc_min_interval_ms.
|
|
|
|
|
|
max_size
|
|
--------
|
|
|
|
Maximum size of the routing cache. Old entries will be purged once the cache
|
|
reached has this size.
|
|
|
|
redirect_load, redirect_number
|
|
------------------------------
|
|
|
|
Factors which determine if more ICPM redirects should be sent to a specific
|
|
host. No redirects will be sent once the load limit or the maximum number of
|
|
redirects has been reached.
|
|
|
|
redirect_silence
|
|
----------------
|
|
|
|
Timeout for redirects. After this period redirects will be sent again, even if
|
|
this has been stopped, because the load or number limit has been reached.
|
|
|
|
Network Neighbor handling
|
|
-------------------------
|
|
|
|
Settings about how to handle connections with direct neighbors (nodes attached
|
|
to the same link) can be found in the directory /proc/sys/net/ipv4/neigh.
|
|
|
|
As we saw it in the conf directory, there is a default subdirectory which
|
|
holds the default values, and one directory for each interface. The contents
|
|
of the directories are identical, with the single exception that the default
|
|
settings contain additional options to set garbage collection parameters.
|
|
|
|
In the interface directories you'll find the following entries:
|
|
|
|
base_reachable_time, base_reachable_time_ms
|
|
-------------------------------------------
|
|
|
|
A base value used for computing the random reachable time value as specified
|
|
in RFC2461.
|
|
|
|
Expression of base_reachable_time, which is deprecated, is in seconds.
|
|
Expression of base_reachable_time_ms is in milliseconds.
|
|
|
|
retrans_time, retrans_time_ms
|
|
-----------------------------
|
|
|
|
The time between retransmitted Neighbor Solicitation messages.
|
|
Used for address resolution and to determine if a neighbor is
|
|
unreachable.
|
|
|
|
Expression of retrans_time, which is deprecated, is in 1/100 seconds (for
|
|
IPv4) or in jiffies (for IPv6).
|
|
Expression of retrans_time_ms is in milliseconds.
|
|
|
|
unres_qlen
|
|
----------
|
|
|
|
Maximum queue length for a pending arp request - the number of packets which
|
|
are accepted from other layers while the ARP address is still resolved.
|
|
|
|
anycast_delay
|
|
-------------
|
|
|
|
Maximum for random delay of answers to neighbor solicitation messages in
|
|
jiffies (1/100 sec). Not yet implemented (Linux does not have anycast support
|
|
yet).
|
|
|
|
ucast_solicit
|
|
-------------
|
|
|
|
Maximum number of retries for unicast solicitation.
|
|
|
|
mcast_solicit
|
|
-------------
|
|
|
|
Maximum number of retries for multicast solicitation.
|
|
|
|
delay_first_probe_time
|
|
----------------------
|
|
|
|
Delay for the first time probe if the neighbor is reachable. (see
|
|
gc_stale_time)
|
|
|
|
locktime
|
|
--------
|
|
|
|
An ARP/neighbor entry is only replaced with a new one if the old is at least
|
|
locktime old. This prevents ARP cache thrashing.
|
|
|
|
proxy_delay
|
|
-----------
|
|
|
|
Maximum time (real time is random [0..proxytime]) before answering to an ARP
|
|
request for which we have an proxy ARP entry. In some cases, this is used to
|
|
prevent network flooding.
|
|
|
|
proxy_qlen
|
|
----------
|
|
|
|
Maximum queue length of the delayed proxy arp timer. (see proxy_delay).
|
|
|
|
app_solicit
|
|
----------
|
|
|
|
Determines the number of requests to send to the user level ARP daemon. Use 0
|
|
to turn off.
|
|
|
|
gc_stale_time
|
|
-------------
|
|
|
|
Determines how often to check for stale ARP entries. After an ARP entry is
|
|
stale it will be resolved again (which is useful when an IP address migrates
|
|
to another machine). When ucast_solicit is greater than 0 it first tries to
|
|
send an ARP packet directly to the known host When that fails and
|
|
mcast_solicit is greater than 0, an ARP request is broadcasted.
|
|
|
|
2.9 Appletalk
|
|
-------------
|
|
|
|
The /proc/sys/net/appletalk directory holds the Appletalk configuration data
|
|
when Appletalk is loaded. The configurable parameters are:
|
|
|
|
aarp-expiry-time
|
|
----------------
|
|
|
|
The amount of time we keep an ARP entry before expiring it. Used to age out
|
|
old hosts.
|
|
|
|
aarp-resolve-time
|
|
-----------------
|
|
|
|
The amount of time we will spend trying to resolve an Appletalk address.
|
|
|
|
aarp-retransmit-limit
|
|
---------------------
|
|
|
|
The number of times we will retransmit a query before giving up.
|
|
|
|
aarp-tick-time
|
|
--------------
|
|
|
|
Controls the rate at which expires are checked.
|
|
|
|
The directory /proc/net/appletalk holds the list of active Appletalk sockets
|
|
on a machine.
|
|
|
|
The fields indicate the DDP type, the local address (in network:node format)
|
|
the remote address, the size of the transmit pending queue, the size of the
|
|
received queue (bytes waiting for applications to read) the state and the uid
|
|
owning the socket.
|
|
|
|
/proc/net/atalk_iface lists all the interfaces configured for appletalk.It
|
|
shows the name of the interface, its Appletalk address, the network range on
|
|
that address (or network number for phase 1 networks), and the status of the
|
|
interface.
|
|
|
|
/proc/net/atalk_route lists each known network route. It lists the target
|
|
(network) that the route leads to, the router (may be directly connected), the
|
|
route flags, and the device the route is using.
|
|
|
|
2.10 IPX
|
|
--------
|
|
|
|
The IPX protocol has no tunable values in proc/sys/net.
|
|
|
|
The IPX protocol does, however, provide proc/net/ipx. This lists each IPX
|
|
socket giving the local and remote addresses in Novell format (that is
|
|
network:node:port). In accordance with the strange Novell tradition,
|
|
everything but the port is in hex. Not_Connected is displayed for sockets that
|
|
are not tied to a specific remote address. The Tx and Rx queue sizes indicate
|
|
the number of bytes pending for transmission and reception. The state
|
|
indicates the state the socket is in and the uid is the owning uid of the
|
|
socket.
|
|
|
|
The /proc/net/ipx_interface file lists all IPX interfaces. For each interface
|
|
it gives the network number, the node number, and indicates if the network is
|
|
the primary network. It also indicates which device it is bound to (or
|
|
Internal for internal networks) and the Frame Type if appropriate. Linux
|
|
supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for
|
|
IPX.
|
|
|
|
The /proc/net/ipx_route table holds a list of IPX routes. For each route it
|
|
gives the destination network, the router node (or Directly) and the network
|
|
address of the router (or Connected) for internal networks.
|
|
|
|
2.11 /proc/sys/fs/mqueue - POSIX message queues filesystem
|
|
----------------------------------------------------------
|
|
|
|
The "mqueue" filesystem provides the necessary kernel features to enable the
|
|
creation of a user space library that implements the POSIX message queues
|
|
API (as noted by the MSG tag in the POSIX 1003.1-2001 version of the System
|
|
Interfaces specification.)
|
|
|
|
The "mqueue" filesystem contains values for determining/setting the amount of
|
|
resources used by the file system.
|
|
|
|
/proc/sys/fs/mqueue/queues_max is a read/write file for setting/getting the
|
|
maximum number of message queues allowed on the system.
|
|
|
|
/proc/sys/fs/mqueue/msg_max is a read/write file for setting/getting the
|
|
maximum number of messages in a queue value. In fact it is the limiting value
|
|
for another (user) limit which is set in mq_open invocation. This attribute of
|
|
a queue must be less or equal then msg_max.
|
|
|
|
/proc/sys/fs/mqueue/msgsize_max is a read/write file for setting/getting the
|
|
maximum message size value (it is every message queue's attribute set during
|
|
its creation).
|
|
|
|
2.12 /proc/<pid>/oom_adj - Adjust the oom-killer score
|
|
------------------------------------------------------
|
|
|
|
This file can be used to adjust the score used to select which processes
|
|
should be killed in an out-of-memory situation. Giving it a high score will
|
|
increase the likelihood of this process being killed by the oom-killer. Valid
|
|
values are in the range -16 to +15, plus the special value -17, which disables
|
|
oom-killing altogether for this process.
|
|
|
|
2.13 /proc/<pid>/oom_score - Display current oom-killer score
|
|
-------------------------------------------------------------
|
|
|
|
------------------------------------------------------------------------------
|
|
This file can be used to check the current score used by the oom-killer is for
|
|
any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which
|
|
process should be killed in an out-of-memory situation.
|
|
|
|
------------------------------------------------------------------------------
|
|
Summary
|
|
------------------------------------------------------------------------------
|
|
Certain aspects of kernel behavior can be modified at runtime, without the
|
|
need to recompile the kernel, or even to reboot the system. The files in the
|
|
/proc/sys tree can not only be read, but also modified. You can use the echo
|
|
command to write value into these files, thereby changing the default settings
|
|
of the kernel.
|
|
------------------------------------------------------------------------------
|
|
|
|
2.14 /proc/<pid>/io - Display the IO accounting fields
|
|
-------------------------------------------------------
|
|
|
|
This file contains IO statistics for each running process
|
|
|
|
Example
|
|
-------
|
|
|
|
test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
|
|
[1] 3828
|
|
|
|
test:/tmp # cat /proc/3828/io
|
|
rchar: 323934931
|
|
wchar: 323929600
|
|
syscr: 632687
|
|
syscw: 632675
|
|
read_bytes: 0
|
|
write_bytes: 323932160
|
|
cancelled_write_bytes: 0
|
|
|
|
|
|
Description
|
|
-----------
|
|
|
|
rchar
|
|
-----
|
|
|
|
I/O counter: chars read
|
|
The number of bytes which this task has caused to be read from storage. This
|
|
is simply the sum of bytes which this process passed to read() and pread().
|
|
It includes things like tty IO and it is unaffected by whether or not actual
|
|
physical disk IO was required (the read might have been satisfied from
|
|
pagecache)
|
|
|
|
|
|
wchar
|
|
-----
|
|
|
|
I/O counter: chars written
|
|
The number of bytes which this task has caused, or shall cause to be written
|
|
to disk. Similar caveats apply here as with rchar.
|
|
|
|
|
|
syscr
|
|
-----
|
|
|
|
I/O counter: read syscalls
|
|
Attempt to count the number of read I/O operations, i.e. syscalls like read()
|
|
and pread().
|
|
|
|
|
|
syscw
|
|
-----
|
|
|
|
I/O counter: write syscalls
|
|
Attempt to count the number of write I/O operations, i.e. syscalls like
|
|
write() and pwrite().
|
|
|
|
|
|
read_bytes
|
|
----------
|
|
|
|
I/O counter: bytes read
|
|
Attempt to count the number of bytes which this process really did cause to
|
|
be fetched from the storage layer. Done at the submit_bio() level, so it is
|
|
accurate for block-backed filesystems. <please add status regarding NFS and
|
|
CIFS at a later time>
|
|
|
|
|
|
write_bytes
|
|
-----------
|
|
|
|
I/O counter: bytes written
|
|
Attempt to count the number of bytes which this process caused to be sent to
|
|
the storage layer. This is done at page-dirtying time.
|
|
|
|
|
|
cancelled_write_bytes
|
|
---------------------
|
|
|
|
The big inaccuracy here is truncate. If a process writes 1MB to a file and
|
|
then deletes the file, it will in fact perform no writeout. But it will have
|
|
been accounted as having caused 1MB of write.
|
|
In other words: The number of bytes which this process caused to not happen,
|
|
by truncating pagecache. A task can cause "negative" IO too. If this task
|
|
truncates some dirty pagecache, some IO which another task has been accounted
|
|
for (in it's write_bytes) will not be happening. We _could_ just subtract that
|
|
from the truncating task's write_bytes, but there is information loss in doing
|
|
that.
|
|
|
|
|
|
Note
|
|
----
|
|
|
|
At its current implementation state, this is a bit racy on 32-bit machines: if
|
|
process A reads process B's /proc/pid/io while process B is updating one of
|
|
those 64-bit counters, process A could see an intermediate result.
|
|
|
|
|
|
More information about this can be found within the taskstats documentation in
|
|
Documentation/accounting.
|
|
|
|
2.15 /proc/<pid>/coredump_filter - Core dump filtering settings
|
|
---------------------------------------------------------------
|
|
When a process is dumped, all anonymous memory is written to a core file as
|
|
long as the size of the core file isn't limited. But sometimes we don't want
|
|
to dump some memory segments, for example, huge shared memory. Conversely,
|
|
sometimes we want to save file-backed memory segments into a core file, not
|
|
only the individual files.
|
|
|
|
/proc/<pid>/coredump_filter allows you to customize which memory segments
|
|
will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
|
|
of memory types. If a bit of the bitmask is set, memory segments of the
|
|
corresponding memory type are dumped, otherwise they are not dumped.
|
|
|
|
The following 4 memory types are supported:
|
|
- (bit 0) anonymous private memory
|
|
- (bit 1) anonymous shared memory
|
|
- (bit 2) file-backed private memory
|
|
- (bit 3) file-backed shared memory
|
|
|
|
Note that MMIO pages such as frame buffer are never dumped and vDSO pages
|
|
are always dumped regardless of the bitmask status.
|
|
|
|
Default value of coredump_filter is 0x3; this means all anonymous memory
|
|
segments are dumped.
|
|
|
|
If you don't want to dump all shared memory segments attached to pid 1234,
|
|
write 1 to the process's proc file.
|
|
|
|
$ echo 0x1 > /proc/1234/coredump_filter
|
|
|
|
When a new process is created, the process inherits the bitmask status from its
|
|
parent. It is useful to set up coredump_filter before the program runs.
|
|
For example:
|
|
|
|
$ echo 0x7 > /proc/self/coredump_filter
|
|
$ ./some_program
|
|
|
|
2.16 /proc/<pid>/mountinfo - Information about mounts
|
|
--------------------------------------------------------
|
|
|
|
This file contains lines of the form:
|
|
|
|
36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
|
|
(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
|
|
|
|
(1) mount ID: unique identifier of the mount (may be reused after umount)
|
|
(2) parent ID: ID of parent (or of self for the top of the mount tree)
|
|
(3) major:minor: value of st_dev for files on filesystem
|
|
(4) root: root of the mount within the filesystem
|
|
(5) mount point: mount point relative to the process's root
|
|
(6) mount options: per mount options
|
|
(7) optional fields: zero or more fields of the form "tag[:value]"
|
|
(8) separator: marks the end of the optional fields
|
|
(9) filesystem type: name of filesystem of the form "type[.subtype]"
|
|
(10) mount source: filesystem specific information or "none"
|
|
(11) super options: per super block options
|
|
|
|
Parsers should ignore all unrecognised optional fields. Currently the
|
|
possible optional fields are:
|
|
|
|
shared:X mount is shared in peer group X
|
|
master:X mount is slave to peer group X
|
|
propagate_from:X mount is slave and receives propagation from peer group X (*)
|
|
unbindable mount is unbindable
|
|
|
|
(*) X is the closest dominant peer group under the process's root. If
|
|
X is the immediate master of the mount, or if there's no dominant peer
|
|
group under the same root, then only the "master:X" field is present
|
|
and not the "propagate_from:X" field.
|
|
|
|
For more information on mount propagation see:
|
|
|
|
Documentation/filesystems/sharedsubtree.txt
|
|
|
|
------------------------------------------------------------------------------
|