linux/include/asm-xtensa
Badari Pulavarty f6b3ec238d [PATCH] madvise(MADV_REMOVE): remove pages from tmpfs shm backing store
Here is the patch to implement madvise(MADV_REMOVE) - which frees up a
given range of pages & its associated backing store.  Current
implementation supports only shmfs/tmpfs and other filesystems return
-ENOSYS.

"Some app allocates large tmpfs files, then when some task quits and some
client disconnect, some memory can be released.  However the only way to
release tmpfs-swap is to MADV_REMOVE". - Andrea Arcangeli

Databases want to use this feature to drop a section of their bufferpool
(shared memory segments) - without writing back to disk/swap space.

This feature is also useful for supporting hot-plug memory on UML.

Concerns raised by Andrew Morton:

- "We have no plan for holepunching!  If we _do_ have such a plan (or
  might in the future) then what would the API look like?  I think
  sys_holepunch(fd, start, len), so we should start out with that."

- Using madvise is very weird, because people will ask "why do I need to
  mmap my file before I can stick a hole in it?"

- None of the other madvise operations call into the filesystem in this
  manner.  A broad question is: is this capability an MM operation or a
  filesytem operation?  truncate, for example, is a filesystem operation
  which sometimes has MM side-effects.  madvise is an mm operation and with
  this patch, it gains FS side-effects, only they're really, really
  significant ones."

Comments:

- Andrea suggested the fs operation too but then it's more efficient to
  have it as a mm operation with fs side effects, because they don't
  immediatly know fd and physical offset of the range.  It's possible to
  fixup in userland and to use the fs operation but it's more expensive,
  the vmas are already in the kernel and we can use them.

Short term plan &  Future Direction:

- We seem to need this interface only for shmfs/tmpfs files in the short
  term.  We have to add hooks into the filesystem for correctness and
  completeness.  This is what this patch does.

- In the future, plan is to support both fs and mmap apis also.  This
  also involves (other) filesystem specific functions to be implemented.

- Current patch doesn't support VM_NONLINEAR - which can be addressed in
  the future.

Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Andrea Arcangeli <andrea@suse.de>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-06 08:33:22 -08:00
..
platform-iss [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 8 2005-06-24 00:05:22 -07:00
xtensa [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 7 2005-06-24 00:05:22 -07:00
a.out.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
atomic.h [PATCH] atomic: inc_not_zero 2005-11-13 18:14:16 -08:00
auxvec.h [PATCH] auxiliary vector cleanups 2005-09-07 16:57:21 -07:00
bitops.h [FLS64]: generic version 2006-01-03 13:11:06 -08:00
bootparam.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
bug.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
bugs.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
byteorder.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
cache.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
cacheflush.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
checksum.h [PATCH] xtensa: replace 'extern inline' with 'static inline' 2005-09-05 00:06:25 -07:00
coprocessor.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
cpumask.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
cputime.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
current.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
delay.h [PATCH] xtensa: replace 'extern inline' with 'static inline' 2005-09-05 00:06:25 -07:00
div64.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
dma-mapping.h [PATCH] gfp_t: dma-mapping (xtensa) 2005-10-28 08:16:49 -07:00
dma.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
elf.h [PATCH] fix remaining missing includes 2005-11-07 07:53:41 -08:00
emergency-restart.h [PATCH] Add emergency_restart() 2005-07-26 14:35:41 -07:00
errno.h [PATCH] xtensa: cleanups for errno and ipc. 2005-06-30 08:45:10 -07:00
fcntl.h [PATCH] Clean up struct flock64 definitions 2005-09-07 16:57:38 -07:00
fixmap.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
hardirq.h [PATCH] xtensa: remove io_remap_page_range and minor clean-ups 2005-09-22 22:17:37 -07:00
highmem.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
hw_irq.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
ide.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
io.h [PATCH] xtensa: replace 'extern inline' with 'static inline' 2005-09-05 00:06:25 -07:00
ioctl.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
ioctls.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
ipcbuf.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
irq.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
kmap_types.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
linkage.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
local.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
mman.h [PATCH] madvise(MADV_REMOVE): remove pages from tmpfs shm backing store 2006-01-06 08:33:22 -08:00
mmu_context.h [PATCH] xtensa: replace 'extern inline' with 'static inline' 2005-09-05 00:06:25 -07:00
mmu.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
module.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
msgbuf.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
namei.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
page.h [PATCH] xtensa: replace 'extern inline' with 'static inline' 2005-09-05 00:06:25 -07:00
param.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
pci-bridge.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
pci.h [PATCH] xtensa: replace 'extern inline' with 'static inline' 2005-09-05 00:06:25 -07:00
percpu.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
pgalloc.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
pgtable.h [PATCH] fix remaining missing includes 2005-11-07 07:53:41 -08:00
platform.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 8 2005-06-24 00:05:22 -07:00
poll.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
posix_types.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
processor.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
ptrace.h kbuild: m68k,parisc,ppc,ppc64,s390,xtensa use generic asm-offsets.h support 2005-09-09 20:57:26 +02:00
resource.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
rmap.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
rwsem.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
scatterlist.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
sections.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
segment.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
semaphore.h [PATCH] xtensa: struct semaphore.sleepers initialization 2005-11-07 07:53:32 -08:00
sembuf.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
serial.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
setup.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
shmbuf.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
shmparam.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
sigcontext.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
siginfo.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
signal.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
smp.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
socket.h [NET]: Introduce SO_{SND,RCV}BUFFORCE socket options 2005-08-29 15:31:35 -07:00
sockios.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
spinlock.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
stat.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
statfs.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
string.h [PATCH] xtensa: replace 'extern inline' with 'static inline' 2005-09-05 00:06:25 -07:00
system.h [PATCH] xtensa: remove io_remap_page_range and minor clean-ups 2005-09-22 22:17:37 -07:00
termbits.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
termios.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
thread_info.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
timex.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
tlb.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
tlbflush.h [PATCH] xtensa: replace 'extern inline' with 'static inline' 2005-09-05 00:06:25 -07:00
topology.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
types.h [PATCH] sab: consolidate kmem_bufctl_t 2005-09-05 00:05:48 -07:00
uaccess.h kbuild: m68k,parisc,ppc,ppc64,s390,xtensa use generic asm-offsets.h support 2005-09-09 20:57:26 +02:00
ucontext.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
unaligned.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
unistd.h [PATCH] xtensa: remove old syscalls 2005-07-07 18:23:44 -07:00
user.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
vga.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00
xor.h [PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6 2005-06-24 00:05:22 -07:00