From 703b3ed55e7a0f1d895800943bfa64fb52a0fec1 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Thu, 9 Apr 2020 14:12:38 +1200 Subject: [PATCH] Support DSM segments in the main shmem area. Create an optional region in the main shared memory segment that can be used to acquire and release "fast" DSM segments, and can benefit from huge pages allocated at cluster startup time, if configured. Fall back to the existing mechanisms when that space is full. The size is controlled by dynamic_shared_memory_main_size, defaulting to 0 (disabled). Main region DSM segments initially contain whatever garbage the memory held last time they were used, rather than zeroes. That change revealed that DSA areas failed to initialize themselves correctly in memory that wasn't zeroed first, so fix that problem. --- src/backend/storage/ipc/dsm.c | 185 +++++++++++++++++++++++++---- src/backend/storage/ipc/dsm_impl.c | 3 + src/backend/storage/ipc/ipci.c | 3 + src/backend/utils/misc/guc.c | 11 ++ src/backend/utils/mmgr/dsa.c | 5 +- src/include/storage/dsm.h | 3 + src/include/storage/dsm_impl.h | 1 + 7 files changed, 186 insertions(+), 25 deletions(-) diff --git a/src/backend/storage/ipc/dsm.c b/src/backend/storage/ipc/dsm.c index ef64d08357..98ae3f341c 100644 --- a/src/backend/storage/ipc/dsm.c +++ b/src/backend/storage/ipc/dsm.c @@ -35,10 +35,12 @@ #include "lib/ilist.h" #include "miscadmin.h" +#include "port/pg_bitutils.h" #include "storage/dsm.h" #include "storage/ipc.h" #include "storage/lwlock.h" #include "storage/pg_shmem.h" +#include "utils/freepage.h" #include "utils/guc.h" #include "utils/memutils.h" #include "utils/resowner_private.h" @@ -76,6 +78,8 @@ typedef struct dsm_control_item { dsm_handle handle; uint32 refcnt; /* 2+ = active, 1 = moribund, 0 = gone */ + size_t first_page; + size_t npages; void *impl_private_pm_handle; /* only needed on Windows */ bool pinned; } dsm_control_item; @@ -95,10 +99,15 @@ static dsm_segment *dsm_create_descriptor(void); static bool dsm_control_segment_sane(dsm_control_header *control, Size mapped_size); static uint64 dsm_control_bytes_needed(uint32 nitems); +static inline dsm_handle make_main_region_dsm_handle(int slot); +static inline bool is_main_region_dsm_handle(dsm_handle handle); /* Has this backend initialized the dynamic shared memory system yet? */ static bool dsm_init_done = false; +/* The address range of DSM space in the main shared memory segment. */ +static void *dsm_main_space_begin = NULL; + /* * List of dynamic shared memory segments used by this backend. * @@ -247,8 +256,12 @@ dsm_cleanup_using_control_segment(dsm_handle old_control_handle) if (refcnt == 0) continue; - /* Log debugging information. */ + /* If it was using the main shmem area, there is nothing to do. */ handle = old_control->item[i].handle; + if (is_main_region_dsm_handle(handle)) + continue; + + /* Log debugging information. */ elog(DEBUG2, "cleaning up orphaned dynamic shared memory with ID %u (reference count %u)", handle, refcnt); @@ -348,8 +361,11 @@ dsm_postmaster_shutdown(int code, Datum arg) if (dsm_control->item[i].refcnt == 0) continue; - /* Log debugging information. */ handle = dsm_control->item[i].handle; + if (is_main_region_dsm_handle(handle)) + continue; + + /* Log debugging information. */ elog(DEBUG2, "cleaning up orphaned dynamic shared memory with ID %u", handle); @@ -418,6 +434,45 @@ dsm_set_control_handle(dsm_handle h) } #endif +/* + * Reserve space in the main shared memory segment for DSM segments. + */ +size_t +dsm_estimate_size(void) +{ + return 1024 * 1024 * (size_t) dynamic_shared_memory_main_size; +} + +/* + * Initialize space in the main shared memory segment for DSM segments. + */ +void +dsm_shmem_init(void) +{ + size_t size = dsm_estimate_size(); + bool found; + + if (size == 0) + return; + + dsm_main_space_begin = ShmemInitStruct("DSM Main Space", size, &found); + if (!found) + { + FreePageManager *fpm = (FreePageManager *) dsm_main_space_begin; + size_t first_page = 0; + size_t pages; + + /* Reserve space for the FreePageManager. */ + while (first_page * FPM_PAGE_SIZE < sizeof(FreePageManager)) + ++first_page; + + /* Initialize it and give it all the rest of the space. */ + FreePageManagerInitialize(fpm, dsm_main_space_begin); + pages = (size / FPM_PAGE_SIZE) - first_page; + FreePageManagerPut(fpm, first_page, pages); + } +} + /* * Create a new dynamic shared memory segment. * @@ -434,6 +489,10 @@ dsm_create(Size size, int flags) dsm_segment *seg; uint32 i; uint32 nitems; + size_t npages = 0; + size_t first_page = 0; + FreePageManager *dsm_main_space_fpm = dsm_main_space_begin; + bool using_main_dsm_region = false; /* Unsafe in postmaster (and pointless in a stand-alone backend). */ Assert(IsUnderPostmaster); @@ -444,20 +503,48 @@ dsm_create(Size size, int flags) /* Create a new segment descriptor. */ seg = dsm_create_descriptor(); - /* Loop until we find an unused segment identifier. */ - for (;;) + /* + * Lock the control segment while we try to allocate from the main + * shared memory area, if configured. + */ + if (dsm_main_space_fpm) { - Assert(seg->mapped_address == NULL && seg->mapped_size == 0); - seg->handle = random(); - if (seg->handle == DSM_HANDLE_INVALID) /* Reserve sentinel */ - continue; - if (dsm_impl_op(DSM_OP_CREATE, seg->handle, size, &seg->impl_private, - &seg->mapped_address, &seg->mapped_size, ERROR)) - break; + npages = size / FPM_PAGE_SIZE; + if (size % FPM_PAGE_SIZE > 0) + ++npages; + + LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE); + if (FreePageManagerGet(dsm_main_space_fpm, npages, &first_page)) + { + /* We can carve out a piece of the main shared memory segment. */ + seg->mapped_address = (char *) dsm_main_space_begin + + first_page * FPM_PAGE_SIZE; + seg->mapped_size = npages * FPM_PAGE_SIZE; + using_main_dsm_region = true; + /* We'll choose a handle below. */ + } } - /* Lock the control segment so we can register the new segment. */ - LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE); + if (!using_main_dsm_region) + { + /* + * We need to create a new memory segment. Loop until we find an + * unused segment identifier. + */ + if (dsm_main_space_fpm) + LWLockRelease(DynamicSharedMemoryControlLock); + for (;;) + { + Assert(seg->mapped_address == NULL && seg->mapped_size == 0); + seg->handle = random() & ~1; /* Even numbers only */ + if (seg->handle == DSM_HANDLE_INVALID) /* Reserve sentinel */ + continue; + if (dsm_impl_op(DSM_OP_CREATE, seg->handle, size, &seg->impl_private, + &seg->mapped_address, &seg->mapped_size, ERROR)) + break; + } + LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE); + } /* Search the control segment for an unused slot. */ nitems = dsm_control->nitems; @@ -465,6 +552,14 @@ dsm_create(Size size, int flags) { if (dsm_control->item[i].refcnt == 0) { + if (using_main_dsm_region) + { + seg->handle = make_main_region_dsm_handle(i); + dsm_control->item[i].first_page = first_page; + dsm_control->item[i].npages = npages; + } + else + Assert(!is_main_region_dsm_handle(seg->handle)); dsm_control->item[i].handle = seg->handle; /* refcnt of 1 triggers destruction, so start at 2 */ dsm_control->item[i].refcnt = 2; @@ -479,9 +574,12 @@ dsm_create(Size size, int flags) /* Verify that we can support an additional mapping. */ if (nitems >= dsm_control->maxitems) { + if (using_main_dsm_region) + FreePageManagerPut(dsm_main_space_fpm, first_page, npages); LWLockRelease(DynamicSharedMemoryControlLock); - dsm_impl_op(DSM_OP_DESTROY, seg->handle, 0, &seg->impl_private, - &seg->mapped_address, &seg->mapped_size, WARNING); + if (!using_main_dsm_region) + dsm_impl_op(DSM_OP_DESTROY, seg->handle, 0, &seg->impl_private, + &seg->mapped_address, &seg->mapped_size, WARNING); if (seg->resowner != NULL) ResourceOwnerForgetDSM(seg->resowner, seg); dlist_delete(&seg->node); @@ -495,6 +593,12 @@ dsm_create(Size size, int flags) } /* Enter the handle into a new array slot. */ + if (using_main_dsm_region) + { + seg->handle = make_main_region_dsm_handle(nitems); + dsm_control->item[i].first_page = first_page; + dsm_control->item[i].npages = npages; + } dsm_control->item[nitems].handle = seg->handle; /* refcnt of 1 triggers destruction, so start at 2 */ dsm_control->item[nitems].refcnt = 2; @@ -580,6 +684,12 @@ dsm_attach(dsm_handle h) /* Otherwise we've found a match. */ dsm_control->item[i].refcnt++; seg->control_slot = i; + if (is_main_region_dsm_handle(seg->handle)) + { + seg->mapped_address = (char *) dsm_main_space_begin + + dsm_control->item[i].first_page * FPM_PAGE_SIZE; + seg->mapped_size = dsm_control->item[i].npages * FPM_PAGE_SIZE; + } break; } LWLockRelease(DynamicSharedMemoryControlLock); @@ -597,8 +707,9 @@ dsm_attach(dsm_handle h) } /* Here's where we actually try to map the segment. */ - dsm_impl_op(DSM_OP_ATTACH, seg->handle, 0, &seg->impl_private, - &seg->mapped_address, &seg->mapped_size, ERROR); + if (!is_main_region_dsm_handle(seg->handle)) + dsm_impl_op(DSM_OP_ATTACH, seg->handle, 0, &seg->impl_private, + &seg->mapped_address, &seg->mapped_size, ERROR); return seg; } @@ -688,8 +799,9 @@ dsm_detach(dsm_segment *seg) */ if (seg->mapped_address != NULL) { - dsm_impl_op(DSM_OP_DETACH, seg->handle, 0, &seg->impl_private, - &seg->mapped_address, &seg->mapped_size, WARNING); + if (!is_main_region_dsm_handle(seg->handle)) + dsm_impl_op(DSM_OP_DETACH, seg->handle, 0, &seg->impl_private, + &seg->mapped_address, &seg->mapped_size, WARNING); seg->impl_private = NULL; seg->mapped_address = NULL; seg->mapped_size = 0; @@ -729,10 +841,15 @@ dsm_detach(dsm_segment *seg) * other reason, the postmaster may not have any better luck than * we did. There's not much we can do about that, though. */ - if (dsm_impl_op(DSM_OP_DESTROY, seg->handle, 0, &seg->impl_private, + if (is_main_region_dsm_handle(seg->handle) || + dsm_impl_op(DSM_OP_DESTROY, seg->handle, 0, &seg->impl_private, &seg->mapped_address, &seg->mapped_size, WARNING)) { LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE); + if (is_main_region_dsm_handle(seg->handle)) + FreePageManagerPut((FreePageManager *) dsm_main_space_begin, + dsm_control->item[control_slot].first_page, + dsm_control->item[control_slot].npages); Assert(dsm_control->item[control_slot].handle == seg->handle); Assert(dsm_control->item[control_slot].refcnt == 1); dsm_control->item[control_slot].refcnt = 0; @@ -894,10 +1011,15 @@ dsm_unpin_segment(dsm_handle handle) * pass the mapped size, mapped address, and private data as NULL * here. */ - if (dsm_impl_op(DSM_OP_DESTROY, handle, 0, &junk_impl_private, + if (is_main_region_dsm_handle(handle) || + dsm_impl_op(DSM_OP_DESTROY, handle, 0, &junk_impl_private, &junk_mapped_address, &junk_mapped_size, WARNING)) { LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE); + if (is_main_region_dsm_handle(handle)) + FreePageManagerPut((FreePageManager *) dsm_main_space_begin, + dsm_control->item[control_slot].first_page, + dsm_control->item[control_slot].npages); Assert(dsm_control->item[control_slot].handle == handle); Assert(dsm_control->item[control_slot].refcnt == 1); dsm_control->item[control_slot].refcnt = 0; @@ -1094,3 +1216,24 @@ dsm_control_bytes_needed(uint32 nitems) return offsetof(dsm_control_header, item) + sizeof(dsm_control_item) * (uint64) nitems; } + +static inline dsm_handle +make_main_region_dsm_handle(int slot) +{ + /* + * We need to create a handle that doesn't collide with any + * existing extra segment created by dsm_impl_op(), so we'll + * make it odd. It also mustn't collide with any other main + * area pseudo-segment, so we'll include the slot number in + * some of the bits. We also want to make an effort to avoid + * newly created and recently destroyed handles from being + * confused, so we'll make the rest of the bits random. + */ + return 1 | (slot << 1) | (random() << (pg_leftmost_one_pos32(dsm_control->maxitems) + 1)); +} + +static inline bool +is_main_region_dsm_handle(dsm_handle handle) +{ + return handle & 1; +} diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c index 1972aecbed..498361e37e 100644 --- a/src/backend/storage/ipc/dsm_impl.c +++ b/src/backend/storage/ipc/dsm_impl.c @@ -113,6 +113,9 @@ const struct config_enum_entry dynamic_shared_memory_options[] = { /* Implementation selector. */ int dynamic_shared_memory_type; +/* Amount of space reserved for DSM segments in the main area. */ +int dynamic_shared_memory_main_size; + /* Size of buffer to be used for zero-filling. */ #define ZBUFFER_SIZE 8192 diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 427b0d59cd..3c3b102b2b 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -119,6 +119,7 @@ CreateSharedMemoryAndSemaphores(void) size = add_size(size, SpinlockSemaSize()); size = add_size(size, hash_estimate_size(SHMEM_INDEX_SIZE, sizeof(ShmemIndexEnt))); + size = add_size(size, dsm_estimate_size()); size = add_size(size, BufferShmemSize()); size = add_size(size, LockShmemSize()); size = add_size(size, PredicateLockShmemSize()); @@ -208,6 +209,8 @@ CreateSharedMemoryAndSemaphores(void) */ InitShmemIndex(); + dsm_shmem_init(); + /* * Set up xlog, clog, and buffers */ diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 5bdc02fce2..88a8a90775 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -2255,6 +2255,17 @@ static struct config_int ConfigureNamesInt[] = NULL, NULL, NULL }, + { + {"dynamic_shared_memory_main_size", PGC_POSTMASTER, RESOURCES_MEM, + gettext_noop("Amount of dynamic shared memory reserved at startup."), + NULL, + GUC_UNIT_MB + }, + &dynamic_shared_memory_main_size, + 0, 0, MAX_KILOBYTES, + NULL, NULL, NULL + }, + /* * We sometimes multiply the number of shared buffers by two without * checking for overflow, so we mustn't allow more than INT_MAX / 2. diff --git a/src/backend/utils/mmgr/dsa.c b/src/backend/utils/mmgr/dsa.c index b7ad8e62ef..6e5e412429 100644 --- a/src/backend/utils/mmgr/dsa.c +++ b/src/backend/utils/mmgr/dsa.c @@ -1223,6 +1223,7 @@ create_internal(void *place, size_t size, * space. */ control = (dsa_area_control *) place; + memset(place, 0, sizeof(*control)); control->segment_header.magic = DSA_SEGMENT_HEADER_MAGIC ^ control_handle ^ 0; control->segment_header.next = DSA_SEGMENT_INDEX_NONE; @@ -1233,14 +1234,10 @@ create_internal(void *place, size_t size, control->handle = control_handle; control->max_total_segment_size = (size_t) -1; control->total_segment_size = size; - memset(&control->segment_handles[0], 0, - sizeof(dsm_handle) * DSA_MAX_SEGMENTS); control->segment_handles[0] = control_handle; for (i = 0; i < DSA_NUM_SEGMENT_BINS; ++i) control->segment_bins[i] = DSA_SEGMENT_INDEX_NONE; - control->high_segment_index = 0; control->refcnt = 1; - control->freed_segment_counter = 0; control->lwlock_tranche_id = tranche_id; /* diff --git a/src/include/storage/dsm.h b/src/include/storage/dsm.h index 408c0543a6..0455576f4a 100644 --- a/src/include/storage/dsm.h +++ b/src/include/storage/dsm.h @@ -29,6 +29,9 @@ extern void dsm_postmaster_startup(struct PGShmemHeader *); extern void dsm_backend_shutdown(void); extern void dsm_detach_all(void); +extern size_t dsm_estimate_size(void); +extern void dsm_shmem_init(void); + #ifdef EXEC_BACKEND extern void dsm_set_control_handle(dsm_handle h); #endif diff --git a/src/include/storage/dsm_impl.h b/src/include/storage/dsm_impl.h index 562cb781a8..6ad9da30ec 100644 --- a/src/include/storage/dsm_impl.h +++ b/src/include/storage/dsm_impl.h @@ -40,6 +40,7 @@ /* GUC. */ extern int dynamic_shared_memory_type; +extern int dynamic_shared_memory_main_size; /* * Directory for on-disk state. -- 2.20.1