diff options
| -rw-r--r-- | src/backend/port/sysv_shmem.c | 127 | ||||
| -rw-r--r-- | src/backend/postmaster/bgworker.c | 1 |
2 files changed, 82 insertions, 46 deletions
diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 437ae4625dc..e0a5f3771a9 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -3,8 +3,11 @@ * sysv_shmem.c * Implement shared memory using SysV facilities * - * These routines represent a fairly thin layer on top of SysV shared - * memory functionality. + * These routines used to be a fairly thin layer on top of SysV shared + * memory functionality. With the addition of anonymous-shmem logic, + * they're a bit fatter now. We still require a SysV shmem block to + * exist, though, because mmap'd shmem provides no way to find out how + * many processes are attached, which we need for interlocking purposes. * * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California @@ -36,14 +39,44 @@ #include "utils/guc.h" +/* + * As of PostgreSQL 9.3, we normally allocate only a very small amount of + * System V shared memory, and only for the purposes of providing an + * interlock to protect the data directory. The real shared memory block + * is allocated using mmap(). This works around the problem that many + * systems have very low limits on the amount of System V shared memory + * that can be allocated. Even a limit of a few megabytes will be enough + * to run many copies of PostgreSQL without needing to adjust system settings. + * + * We assume that no one will attempt to run PostgreSQL 9.3 or later on + * systems that are ancient enough that anonymous shared memory is not + * supported, such as pre-2.4 versions of Linux. If that turns out to be + * false, we might need to add compile and/or run-time tests here and do this + * only if the running kernel supports it. + * + * However, we must always disable this logic in the EXEC_BACKEND case, and + * fall back to the old method of allocating the entire segment using System V + * shared memory, because there's no way to attach an anonymous mmap'd segment + * to a process after exec(). Since EXEC_BACKEND is intended only for + * developer use, this shouldn't be a big problem. Because of this, we do + * not worry about supporting anonymous shmem in the EXEC_BACKEND cases below. + */ +#ifndef EXEC_BACKEND +#define USE_ANONYMOUS_SHMEM +#endif + + typedef key_t IpcMemoryKey; /* shared memory key passed to shmget(2) */ typedef int IpcMemoryId; /* shared memory ID returned by shmget(2) */ unsigned long UsedShmemSegID = 0; void *UsedShmemSegAddr = NULL; + +#ifdef USE_ANONYMOUS_SHMEM static Size AnonymousShmemSize; static void *AnonymousShmem = NULL; +#endif static void *InternalIpcMemoryCreate(IpcMemoryKey memKey, Size size); static void IpcMemoryDetach(int status, Datum shmaddr); @@ -204,10 +237,6 @@ IpcMemoryDetach(int status, Datum shmaddr) /* Detach System V shared memory block. */ if (shmdt(DatumGetPointer(shmaddr)) < 0) elog(LOG, "shmdt(%p) failed: %m", DatumGetPointer(shmaddr)); - /* Release anonymous shared memory block, if any. */ - if (AnonymousShmem != NULL - && munmap(AnonymousShmem, AnonymousShmemSize) < 0) - elog(LOG, "munmap(%p) failed: %m", AnonymousShmem); } /****************************************************************************/ @@ -318,6 +347,8 @@ PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2) return true; } +#ifdef USE_ANONYMOUS_SHMEM + /* * Creates an anonymous mmap()ed shared memory segment. * @@ -325,7 +356,6 @@ PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2) * actual size of the allocation, if it ends up allocating a segment that is * larger than requested. */ -#ifndef EXEC_BACKEND static void * CreateAnonymousSegment(Size *size) { @@ -334,10 +364,8 @@ CreateAnonymousSegment(Size *size) int mmap_errno = 0; #ifndef MAP_HUGETLB - if (huge_pages == HUGE_PAGES_ON) - ereport(ERROR, - (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), - errmsg("huge TLB pages not supported on this platform"))); + /* PGSharedMemoryCreate should have dealt with this case */ + Assert(huge_pages != HUGE_PAGES_ON); #else if (huge_pages == HUGE_PAGES_ON || huge_pages == HUGE_PAGES_TRY) { @@ -366,12 +394,12 @@ CreateAnonymousSegment(Size *size) PG_MMAP_FLAGS | MAP_HUGETLB, -1, 0); mmap_errno = errno; if (huge_pages == HUGE_PAGES_TRY && ptr == MAP_FAILED) - elog(DEBUG1, "mmap with MAP_HUGETLB failed, huge pages disabled: %m"); + elog(DEBUG1, "mmap(%zu) with MAP_HUGETLB failed, huge pages disabled: %m", + allocsize); } #endif - if (huge_pages == HUGE_PAGES_OFF || - (huge_pages == HUGE_PAGES_TRY && ptr == MAP_FAILED)) + if (ptr == MAP_FAILED && huge_pages != HUGE_PAGES_ON) { /* * use the original size, not the rounded up value, when falling back @@ -401,7 +429,25 @@ CreateAnonymousSegment(Size *size) *size = allocsize; return ptr; } -#endif + +/* + * AnonymousShmemDetach --- detach from an anonymous mmap'd block + * (called as an on_shmem_exit callback, hence funny argument list) + */ +static void +AnonymousShmemDetach(int status, Datum arg) +{ + /* Release anonymous shared memory block, if any. */ + if (AnonymousShmem != NULL) + { + if (munmap(AnonymousShmem, AnonymousShmemSize) < 0) + elog(LOG, "munmap(%p, %zu) failed: %m", + AnonymousShmem, AnonymousShmemSize); + AnonymousShmem = NULL; + } +} + +#endif /* USE_ANONYMOUS_SHMEM */ /* * PGSharedMemoryCreate @@ -432,7 +478,8 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port, struct stat statbuf; Size sysvsize; -#if defined(EXEC_BACKEND) || !defined(MAP_HUGETLB) + /* Complain if hugepages demanded but we can't possibly support them */ +#if !defined(USE_ANONYMOUS_SHMEM) || !defined(MAP_HUGETLB) if (huge_pages == HUGE_PAGES_ON) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), @@ -442,32 +489,13 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port, /* Room for a header? */ Assert(size > MAXALIGN(sizeof(PGShmemHeader))); - /* - * As of PostgreSQL 9.3, we normally allocate only a very small amount of - * System V shared memory, and only for the purposes of providing an - * interlock to protect the data directory. The real shared memory block - * is allocated using mmap(). This works around the problem that many - * systems have very low limits on the amount of System V shared memory - * that can be allocated. Even a limit of a few megabytes will be enough - * to run many copies of PostgreSQL without needing to adjust system - * settings. - * - * We assume that no one will attempt to run PostgreSQL 9.3 or later on - * systems that are ancient enough that anonymous shared memory is not - * supported, such as pre-2.4 versions of Linux. If that turns out to be - * false, we might need to add a run-time test here and do this only if - * the running kernel supports it. - * - * However, we disable this logic in the EXEC_BACKEND case, and fall back - * to the old method of allocating the entire segment using System V - * shared memory, because there's no way to attach an mmap'd segment to a - * process after exec(). Since EXEC_BACKEND is intended only for - * developer use, this shouldn't be a big problem. - */ -#ifndef EXEC_BACKEND +#ifdef USE_ANONYMOUS_SHMEM AnonymousShmem = CreateAnonymousSegment(&size); AnonymousShmemSize = size; + /* Register on-exit routine to unmap the anonymous segment */ + on_shmem_exit(AnonymousShmemDetach, (Datum) 0); + /* Now we need only allocate a minimal-sized SysV shmem block. */ sysvsize = sizeof(PGShmemHeader); #else @@ -572,10 +600,14 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port, * block. Otherwise, the System V shared memory block is only a shim, and * we must return a pointer to the real block. */ +#ifdef USE_ANONYMOUS_SHMEM if (AnonymousShmem == NULL) return hdr; memcpy(AnonymousShmem, hdr, sizeof(PGShmemHeader)); return (PGShmemHeader *) AnonymousShmem; +#else + return hdr; +#endif } #ifdef EXEC_BACKEND @@ -660,12 +692,12 @@ PGSharedMemoryNoReAttach(void) * * Detach from the shared memory segment, if still attached. This is not * intended to be called explicitly by the process that originally created the - * segment (it will have an on_shmem_exit callback registered to do that). + * segment (it will have on_shmem_exit callback(s) registered to do that). * Rather, this is for subprocesses that have inherited an attachment and want * to get rid of it. * * UsedShmemSegID and UsedShmemSegAddr are implicit parameters to this - * routine. + * routine, also AnonymousShmem and AnonymousShmemSize. */ void PGSharedMemoryDetach(void) @@ -682,10 +714,15 @@ PGSharedMemoryDetach(void) UsedShmemSegAddr = NULL; } - /* Release anonymous shared memory block, if any. */ - if (AnonymousShmem != NULL - && munmap(AnonymousShmem, AnonymousShmemSize) < 0) - elog(LOG, "munmap(%p) failed: %m", AnonymousShmem); +#ifdef USE_ANONYMOUS_SHMEM + if (AnonymousShmem != NULL) + { + if (munmap(AnonymousShmem, AnonymousShmemSize) < 0) + elog(LOG, "munmap(%p, %zu) failed: %m", + AnonymousShmem, AnonymousShmemSize); + AnonymousShmem = NULL; + } +#endif } diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c index fd552626684..e32eb3e6669 100644 --- a/src/backend/postmaster/bgworker.c +++ b/src/backend/postmaster/bgworker.c @@ -601,7 +601,6 @@ StartBackgroundWorker(void) */ if ((worker->bgw_flags & BGWORKER_SHMEM_ACCESS) == 0) { - on_exit_reset(); dsm_detach_all(); PGSharedMemoryDetach(); } |