mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-14 08:13:56 +08:00
37a327957e
I couldn't find any docs explaining the contents of /sys/block/<dev>/stat, so I wrote up the following. I'm not completely sure it's accurate - Jens, could you give a yea or nay on this? In particular, the counts of read/write IOs and read/write sectors are incremented in different places - it looks like they both increment as the request is being finished, but I'm not completely sure of that. Cc: Jens Axboe <axboe@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
83 lines
3.2 KiB
Plaintext
83 lines
3.2 KiB
Plaintext
Block layer statistics in /sys/block/<dev>/stat
|
|
===============================================
|
|
|
|
This file documents the contents of the /sys/block/<dev>/stat file.
|
|
|
|
The stat file provides several statistics about the state of block
|
|
device <dev>.
|
|
|
|
Q. Why are there multiple statistics in a single file? Doesn't sysfs
|
|
normally contain a single value per file?
|
|
A. By having a single file, the kernel can guarantee that the statistics
|
|
represent a consistent snapshot of the state of the device. If the
|
|
statistics were exported as multiple files containing one statistic
|
|
each, it would be impossible to guarantee that a set of readings
|
|
represent a single point in time.
|
|
|
|
The stat file consists of a single line of text containing 11 decimal
|
|
values separated by whitespace. The fields are summarized in the
|
|
following table, and described in more detail below.
|
|
|
|
Name units description
|
|
---- ----- -----------
|
|
read I/Os requests number of read I/Os processed
|
|
read merges requests number of read I/Os merged with in-queue I/O
|
|
read sectors sectors number of sectors read
|
|
read ticks milliseconds total wait time for read requests
|
|
write I/Os requests number of write I/Os processed
|
|
write merges requests number of write I/Os merged with in-queue I/O
|
|
write sectors sectors number of sectors written
|
|
write ticks milliseconds total wait time for write requests
|
|
in_flight requests number of I/Os currently in flight
|
|
io_ticks milliseconds total time this block device has been active
|
|
time_in_queue milliseconds total wait time for all requests
|
|
|
|
read I/Os, write I/Os
|
|
=====================
|
|
|
|
These values increment when an I/O request completes.
|
|
|
|
read merges, write merges
|
|
=========================
|
|
|
|
These values increment when an I/O request is merged with an
|
|
already-queued I/O request.
|
|
|
|
read sectors, write sectors
|
|
===========================
|
|
|
|
These values count the number of sectors read from or written to this
|
|
block device. The "sectors" in question are the standard UNIX 512-byte
|
|
sectors, not any device- or filesystem-specific block size. The
|
|
counters are incremented when the I/O completes.
|
|
|
|
read ticks, write ticks
|
|
=======================
|
|
|
|
These values count the number of milliseconds that I/O requests have
|
|
waited on this block device. If there are multiple I/O requests waiting,
|
|
these values will increase at a rate greater than 1000/second; for
|
|
example, if 60 read requests wait for an average of 30 ms, the read_ticks
|
|
field will increase by 60*30 = 1800.
|
|
|
|
in_flight
|
|
=========
|
|
|
|
This value counts the number of I/O requests that have been issued to
|
|
the device driver but have not yet completed. It does not include I/O
|
|
requests that are in the queue but not yet issued to the device driver.
|
|
|
|
io_ticks
|
|
========
|
|
|
|
This value counts the number of milliseconds during which the device has
|
|
had I/O requests queued.
|
|
|
|
time_in_queue
|
|
=============
|
|
|
|
This value counts the number of milliseconds that I/O requests have waited
|
|
on this block device. If there are multiple I/O requests waiting, this
|
|
value will increase as the product of the number of milliseconds times the
|
|
number of requests waiting (see "read ticks" above for an example).
|