linux/include/asm-arm26
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
..
a.out.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
assembler.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -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
bug.h [PATCH] remove all kernel BUGs 2005-05-01 08:59:01 -07:00
bugs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
byteorder.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
cache.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
cacheflush.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
checksum.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
constants.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
cputime.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
current.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
delay.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
div64.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
dma-mapping.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
dma.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ecard.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
elf.h [PATCH] ARM: 2696/1: remove ';' in ELF_DATA define in asm-arm{,26}/elf.h 2005-06-03 20:52:26 +01:00
emergency-restart.h [PATCH] Add emergency_restart() 2005-07-26 14:35:41 -07:00
errno.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
fcntl.h [PATCH] Clean up struct flock64 definitions 2005-09-07 16:57:38 -07:00
fiq.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
floppy.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
fpstate.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
futex.h [PATCH] Remove unused var from asm/futex.h 2005-09-21 16:16:29 -07:00
hardirq.h [PATCH] include/asm-arm26/hardirq.h: remove #define irq_enter() 2005-09-10 10:06:30 -07:00
hardware.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ide.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
io.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ioc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ioctl.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ioctls.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ipc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ipcbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
irq.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
irqchip.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
kmap_types.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
leds.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
limits.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
linkage.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
local.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
locks.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mach-types.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
map.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mc146818rtc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
memory.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -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 Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mmu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
module.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
msgbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
namei.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
oldlatches.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
page.h [PATCH] mm: consolidate get_order 2005-09-05 00:05:39 -07:00
param.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
parport.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pci.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
percpu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgalloc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgtable.h [PATCH] vm: remove unused/broken page_pte[_prot] macros 2005-10-30 17:37:22 -08:00
poll.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
posix_types.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
proc-fns.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
processor.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
procinfo.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ptrace.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
resource.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
scatterlist.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sections.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
segment.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
semaphore-helper.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
semaphore.h [PATCH] semaphore: Remove __MUTEX_INITIALIZER() 2005-10-30 17:37:27 -08:00
sembuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
serial.h [PATCH] Serial: Split 8250 port table (part 2) 2005-06-29 18:45:19 +01:00
setup.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
shmbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
shmparam.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sigcontext.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
siginfo.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
signal.h [PATCH] Remove obsolete HAVE_ARCH_GET_SIGNAL_TO_DELIVER? 2005-06-12 20:43:21 -07:00
sizes.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
smp.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
socket.h [NET]: Introduce SO_{SND,RCV}BUFFORCE socket options 2005-08-29 15:31:35 -07:00
sockios.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
spinlock.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
stat.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
statfs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
string.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
suspend.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sysirq.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
system.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
termbits.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
termios.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
thread_info.h [PATCH] streamline preempt_count type across archs 2005-06-23 09:45:19 -07:00
timex.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
tlb.h [PATCH] mm: tlb_finish_mmu forget rss 2005-10-29 21:40:37 -07:00
tlbflush.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
topology.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
types.h [PATCH] sab: consolidate kmem_bufctl_t 2005-09-05 00:05:48 -07:00
uaccess-asm.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
uaccess.h [PATCH] remove verify_area(): remove verify_area() from various uaccess.h headers 2005-09-07 16:57:35 -07:00
ucontext.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
unaligned.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
uncompress.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
unistd.h [PATCH] unify sys_ptrace prototype 2005-10-30 17:37:20 -08:00
user.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
xor.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00