2005-04-17 06:20:36 +08:00
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#ifndef __ALPHA_MMAN_H__
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#define __ALPHA_MMAN_H__
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#define PROT_READ 0x1 /* page can be read */
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#define PROT_WRITE 0x2 /* page can be written */
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#define PROT_EXEC 0x4 /* page can be executed */
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#define PROT_SEM 0x8 /* page may be used for atomic ops */
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#define PROT_NONE 0x0 /* page can not be accessed */
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#define PROT_GROWSDOWN 0x01000000 /* mprotect flag: extend change to start of growsdown vma */
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#define PROT_GROWSUP 0x02000000 /* mprotect flag: extend change to end of growsup vma */
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#define MAP_SHARED 0x01 /* Share changes */
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#define MAP_PRIVATE 0x02 /* Changes are private */
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#define MAP_TYPE 0x0f /* Mask for type of mapping (OSF/1 is _wrong_) */
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#define MAP_FIXED 0x100 /* Interpret addr exactly */
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#define MAP_ANONYMOUS 0x10 /* don't use a file */
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/* not used by linux, but here to make sure we don't clash with OSF/1 defines */
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#define _MAP_HASSEMAPHORE 0x0200
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#define _MAP_INHERIT 0x0400
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#define _MAP_UNALIGNED 0x0800
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/* These are linux-specific */
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#define MAP_GROWSDOWN 0x01000 /* stack-like segment */
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#define MAP_DENYWRITE 0x02000 /* ETXTBSY */
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#define MAP_EXECUTABLE 0x04000 /* mark it as an executable */
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#define MAP_LOCKED 0x08000 /* lock the mapping */
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#define MAP_NORESERVE 0x10000 /* don't check for reservations */
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#define MAP_POPULATE 0x20000 /* populate (prefault) pagetables */
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#define MAP_NONBLOCK 0x40000 /* do not block on IO */
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#define MS_ASYNC 1 /* sync memory asynchronously */
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#define MS_SYNC 2 /* synchronous memory sync */
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#define MS_INVALIDATE 4 /* invalidate the caches */
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#define MCL_CURRENT 8192 /* lock all currently mapped pages */
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#define MCL_FUTURE 16384 /* lock all additions to address space */
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#define MADV_NORMAL 0 /* no further special treatment */
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#define MADV_RANDOM 1 /* expect random page references */
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#define MADV_SEQUENTIAL 2 /* expect sequential page references */
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#define MADV_WILLNEED 3 /* will need these pages */
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#define MADV_SPACEAVAIL 5 /* ensure resources are available */
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#define MADV_DONTNEED 6 /* don't need these pages */
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[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 16:10:38 +08:00
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#define MADV_REMOVE 7 /* remove these pages & resources */
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2006-02-15 05:53:08 +08:00
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#define MADV_DONTFORK 0x30 /* dont inherit across fork */
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#define MADV_DOFORK 0x31 /* do inherit across fork */
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2005-04-17 06:20:36 +08:00
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/* compatibility flags */
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#define MAP_ANON MAP_ANONYMOUS
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#define MAP_FILE 0
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#endif /* __ALPHA_MMAN_H__ */
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