From f6b3ec238d12c8cc6cc71490c6e3127988460349 Mon Sep 17 00:00:00 2001 From: Badari Pulavarty Date: Fri, 6 Jan 2006 00:10:38 -0800 Subject: [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 Cc: Hugh Dickins Cc: Andrea Arcangeli Cc: Michael Kerrisk Cc: Ulrich Drepper Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-parisc/mman.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/asm-parisc') diff --git a/include/asm-parisc/mman.h b/include/asm-parisc/mman.h index e829607eb8bc..736b0abcac05 100644 --- a/include/asm-parisc/mman.h +++ b/include/asm-parisc/mman.h @@ -38,6 +38,7 @@ #define MADV_SPACEAVAIL 5 /* insure that resources are reserved */ #define MADV_VPS_PURGE 6 /* Purge pages from VM page cache */ #define MADV_VPS_INHERIT 7 /* Inherit parents page size */ +#define MADV_REMOVE 8 /* remove these pages & resources */ /* The range 12-64 is reserved for page size specification. */ #define MADV_4K_PAGES 12 /* Use 4K pages */ -- cgit v1.2.2 From d3cb487149bd706aa6aeb02042332a450978dc1c Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Fri, 6 Jan 2006 00:11:20 -0800 Subject: [PATCH] atomic_long_t & include/asm-generic/atomic.h V2 Several counters already have the need to use 64 atomic variables on 64 bit platforms (see mm_counter_t in sched.h). We have to do ugly ifdefs to fall back to 32 bit atomic on 32 bit platforms. The VM statistics patch that I am working on will also make more extensive use of atomic64. This patch introduces a new type atomic_long_t by providing definitions in asm-generic/atomic.h that works similar to the c "long" type. Its 32 bits on 32 bit platforms and 64 bits on 64 bit platforms. Also cleans up the determination of the mm_counter_t in sched.h. Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-parisc/atomic.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/asm-parisc') diff --git a/include/asm-parisc/atomic.h b/include/asm-parisc/atomic.h index 983e9a2b6042..64ebd086c40d 100644 --- a/include/asm-parisc/atomic.h +++ b/include/asm-parisc/atomic.h @@ -216,4 +216,5 @@ static __inline__ int atomic_read(const atomic_t *v) #define smp_mb__before_atomic_inc() smp_mb() #define smp_mb__after_atomic_inc() smp_mb() +#include #endif -- cgit v1.2.2