diff options
| author | Bruce Momjian | 2015-03-22 02:06:19 +0000 |
|---|---|---|
| committer | Bruce Momjian | 2015-03-22 02:06:19 +0000 |
| commit | 34afbba84e8fd12bbf905d68d1112f51ed584df9 (patch) | |
| tree | a4e66fb4b46745b5996190dc467bdb1b36cc3318 | |
| parent | 9d61b9953c1489cbb458ca70013cf5fca1bb7710 (diff) | |
Use mmap MAP_NOSYNC option to limit shared memory writes
mmap() is rarely used for shared memory, but when it is, this option is
useful, particularly on the BSDs.
Patch by Sean Chittenden
| -rw-r--r-- | src/backend/storage/ipc/dsm_impl.c | 4 | ||||
| -rw-r--r-- | src/include/portability/mem.h | 8 |
2 files changed, 10 insertions, 2 deletions
diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c index cf7938cb44..0859fbfc93 100644 --- a/src/backend/storage/ipc/dsm_impl.c +++ b/src/backend/storage/ipc/dsm_impl.c @@ -368,7 +368,7 @@ dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size, /* Map it. */ address = mmap(NULL, request_size, PROT_READ | PROT_WRITE, - MAP_SHARED | MAP_HASSEMAPHORE, fd, 0); + MAP_SHARED | MAP_HASSEMAPHORE | MAP_NOSYNC, fd, 0); if (address == MAP_FAILED) { int save_errno; @@ -960,7 +960,7 @@ dsm_impl_mmap(dsm_op op, dsm_handle handle, Size request_size, /* Map it. */ address = mmap(NULL, request_size, PROT_READ | PROT_WRITE, - MAP_SHARED | MAP_HASSEMAPHORE, fd, 0); + MAP_SHARED | MAP_HASSEMAPHORE | MAP_NOSYNC, fd, 0); if (address == MAP_FAILED) { int save_errno; diff --git a/src/include/portability/mem.h b/src/include/portability/mem.h index 7c77dbd128..a4b01fecae 100644 --- a/src/include/portability/mem.h +++ b/src/include/portability/mem.h @@ -30,6 +30,14 @@ #define MAP_HASSEMAPHORE 0 #endif +/* + * BSD-derived systems use the MAP_NOSYNC flag to prevent dirty mmap(2) + * pages from being gratuitously flushed to disk. + */ +#ifndef MAP_NOSYNC +#define MAP_NOSYNC 0 +#endif + #define PG_MMAP_FLAGS (MAP_SHARED|MAP_ANONYMOUS|MAP_HASSEMAPHORE) /* Some really old systems don't define MAP_FAILED. */ |