Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * shmem.c
4 : * create shared memory and initialize shared memory data structures.
5 : *
6 : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/storage/ipc/shmem.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : /*
16 : * POSTGRES processes share one or more regions of shared memory.
17 : * The shared memory is created by a postmaster and is inherited
18 : * by each backend via fork() (or, in some ports, via other OS-specific
19 : * methods). The routines in this file are used for allocating and
20 : * binding to shared memory data structures.
21 : *
22 : * NOTES:
23 : * (a) There are three kinds of shared memory data structures
24 : * available to POSTGRES: fixed-size structures, queues and hash
25 : * tables. Fixed-size structures contain things like global variables
26 : * for a module and should never be allocated after the shared memory
27 : * initialization phase. Hash tables have a fixed maximum size, but
28 : * their actual size can vary dynamically. When entries are added
29 : * to the table, more space is allocated. Queues link data structures
30 : * that have been allocated either within fixed-size structures or as hash
31 : * buckets. Each shared data structure has a string name to identify
32 : * it (assigned in the module that declares it).
33 : *
34 : * (b) During initialization, each module looks for its
35 : * shared data structures in a hash table called the "Shmem Index".
36 : * If the data structure is not present, the caller can allocate
37 : * a new one and initialize it. If the data structure is present,
38 : * the caller "attaches" to the structure by initializing a pointer
39 : * in the local address space.
40 : * The shmem index has two purposes: first, it gives us
41 : * a simple model of how the world looks when a backend process
42 : * initializes. If something is present in the shmem index,
43 : * it is initialized. If it is not, it is uninitialized. Second,
44 : * the shmem index allows us to allocate shared memory on demand
45 : * instead of trying to preallocate structures and hard-wire the
46 : * sizes and locations in header files. If you are using a lot
47 : * of shared memory in a lot of different places (and changing
48 : * things during development), this is important.
49 : *
50 : * (c) In standard Unix-ish environments, individual backends do not
51 : * need to re-establish their local pointers into shared memory, because
52 : * they inherit correct values of those variables via fork() from the
53 : * postmaster. However, this does not work in the EXEC_BACKEND case.
54 : * In ports using EXEC_BACKEND, new backends have to set up their local
55 : * pointers using the method described in (b) above.
56 : *
57 : * (d) memory allocation model: shared memory can never be
58 : * freed, once allocated. Each hash table has its own free list,
59 : * so hash buckets can be reused when an item is deleted. However,
60 : * if one hash table grows very large and then shrinks, its space
61 : * cannot be redistributed to other tables. We could build a simple
62 : * hash bucket garbage collector if need be. Right now, it seems
63 : * unnecessary.
64 : */
65 :
66 : #include "postgres.h"
67 :
68 : #include "common/int.h"
69 : #include "fmgr.h"
70 : #include "funcapi.h"
71 : #include "miscadmin.h"
72 : #include "port/pg_numa.h"
73 : #include "storage/lwlock.h"
74 : #include "storage/pg_shmem.h"
75 : #include "storage/shmem.h"
76 : #include "storage/spin.h"
77 : #include "utils/builtins.h"
78 :
79 : /*
80 : * This is the first data structure stored in the shared memory segment, at
81 : * the offset that PGShmemHeader->content_offset points to. Allocations by
82 : * ShmemAlloc() are carved out of the space after this.
83 : *
84 : * For the base pointer and the total size of the shmem segment, we rely on
85 : * the PGShmemHeader.
86 : */
87 : typedef struct ShmemAllocatorData
88 : {
89 : Size free_offset; /* offset to first free space from ShmemBase */
90 : HTAB *index; /* copy of ShmemIndex */
91 :
92 : /* protects shared memory and LWLock allocation */
93 : slock_t shmem_lock;
94 : } ShmemAllocatorData;
95 :
96 : static void *ShmemAllocRaw(Size size, Size *allocated_size);
97 :
98 : /* shared memory global variables */
99 :
100 : static PGShmemHeader *ShmemSegHdr; /* shared mem segment header */
101 : static void *ShmemBase; /* start address of shared memory */
102 : static void *ShmemEnd; /* end+1 address of shared memory */
103 :
104 : static ShmemAllocatorData *ShmemAllocator;
105 : slock_t *ShmemLock; /* points to ShmemAllocator->shmem_lock */
106 : static HTAB *ShmemIndex = NULL; /* primary index hashtable for shmem */
107 :
108 : /* To get reliable results for NUMA inquiry we need to "touch pages" once */
109 : static bool firstNumaTouch = true;
110 :
111 : Datum pg_numa_available(PG_FUNCTION_ARGS);
112 :
113 : /*
114 : * InitShmemAllocator() --- set up basic pointers to shared memory.
115 : *
116 : * Called at postmaster or stand-alone backend startup, to initialize the
117 : * allocator's data structure in the shared memory segment. In EXEC_BACKEND,
118 : * this is also called at backend startup, to set up pointers to the shared
119 : * memory areas.
120 : */
121 : void
122 2280 : InitShmemAllocator(PGShmemHeader *seghdr)
123 : {
124 : Assert(seghdr != NULL);
125 :
126 : /*
127 : * We assume the pointer and offset are MAXALIGN. Not a hard requirement,
128 : * but it's true today and keeps the math below simpler.
129 : */
130 : Assert(seghdr == (void *) MAXALIGN(seghdr));
131 : Assert(seghdr->content_offset == MAXALIGN(seghdr->content_offset));
132 :
133 2280 : ShmemSegHdr = seghdr;
134 2280 : ShmemBase = seghdr;
135 2280 : ShmemEnd = (char *) ShmemBase + seghdr->totalsize;
136 :
137 : #ifndef EXEC_BACKEND
138 : Assert(!IsUnderPostmaster);
139 : #endif
140 2280 : if (IsUnderPostmaster)
141 : {
142 0 : PGShmemHeader *shmhdr = ShmemSegHdr;
143 :
144 0 : ShmemAllocator = (ShmemAllocatorData *) ((char *) shmhdr + shmhdr->content_offset);
145 0 : ShmemLock = &ShmemAllocator->shmem_lock;
146 : }
147 : else
148 : {
149 : Size offset;
150 :
151 : /*
152 : * Allocations after this point should go through ShmemAlloc, which
153 : * expects to allocate everything on cache line boundaries. Make sure
154 : * the first allocation begins on a cache line boundary.
155 : */
156 2280 : offset = CACHELINEALIGN(seghdr->content_offset + sizeof(ShmemAllocatorData));
157 2280 : if (offset > seghdr->totalsize)
158 0 : ereport(ERROR,
159 : (errcode(ERRCODE_OUT_OF_MEMORY),
160 : errmsg("out of shared memory (%zu bytes requested)",
161 : offset)));
162 :
163 2280 : ShmemAllocator = (ShmemAllocatorData *) ((char *) seghdr + seghdr->content_offset);
164 :
165 2280 : SpinLockInit(&ShmemAllocator->shmem_lock);
166 2280 : ShmemLock = &ShmemAllocator->shmem_lock;
167 2280 : ShmemAllocator->free_offset = offset;
168 : /* ShmemIndex can't be set up yet (need LWLocks first) */
169 2280 : ShmemAllocator->index = NULL;
170 2280 : ShmemIndex = (HTAB *) NULL;
171 : }
172 2280 : }
173 :
174 : /*
175 : * ShmemAlloc -- allocate max-aligned chunk from shared memory
176 : *
177 : * Throws error if request cannot be satisfied.
178 : *
179 : * Assumes ShmemLock and ShmemSegHdr are initialized.
180 : */
181 : void *
182 6846 : ShmemAlloc(Size size)
183 : {
184 : void *newSpace;
185 : Size allocated_size;
186 :
187 6846 : newSpace = ShmemAllocRaw(size, &allocated_size);
188 6846 : if (!newSpace)
189 0 : ereport(ERROR,
190 : (errcode(ERRCODE_OUT_OF_MEMORY),
191 : errmsg("out of shared memory (%zu bytes requested)",
192 : size)));
193 6846 : return newSpace;
194 : }
195 :
196 : /*
197 : * ShmemAllocNoError -- allocate max-aligned chunk from shared memory
198 : *
199 : * As ShmemAlloc, but returns NULL if out of space, rather than erroring.
200 : */
201 : void *
202 920326 : ShmemAllocNoError(Size size)
203 : {
204 : Size allocated_size;
205 :
206 920326 : return ShmemAllocRaw(size, &allocated_size);
207 : }
208 :
209 : /*
210 : * ShmemAllocRaw -- allocate align chunk and return allocated size
211 : *
212 : * Also sets *allocated_size to the number of bytes allocated, which will
213 : * be equal to the number requested plus any padding we choose to add.
214 : */
215 : static void *
216 1098170 : ShmemAllocRaw(Size size, Size *allocated_size)
217 : {
218 : Size newStart;
219 : Size newFree;
220 : void *newSpace;
221 :
222 : /*
223 : * Ensure all space is adequately aligned. We used to only MAXALIGN this
224 : * space but experience has proved that on modern systems that is not good
225 : * enough. Many parts of the system are very sensitive to critical data
226 : * structures getting split across cache line boundaries. To avoid that,
227 : * attempt to align the beginning of the allocation to a cache line
228 : * boundary. The calling code will still need to be careful about how it
229 : * uses the allocated space - e.g. by padding each element in an array of
230 : * structures out to a power-of-two size - but without this, even that
231 : * won't be sufficient.
232 : */
233 1098170 : size = CACHELINEALIGN(size);
234 1098170 : *allocated_size = size;
235 :
236 : Assert(ShmemSegHdr != NULL);
237 :
238 1098170 : SpinLockAcquire(ShmemLock);
239 :
240 1098170 : newStart = ShmemAllocator->free_offset;
241 :
242 1098170 : newFree = newStart + size;
243 1098170 : if (newFree <= ShmemSegHdr->totalsize)
244 : {
245 1098170 : newSpace = (char *) ShmemBase + newStart;
246 1098170 : ShmemAllocator->free_offset = newFree;
247 : }
248 : else
249 0 : newSpace = NULL;
250 :
251 1098170 : SpinLockRelease(ShmemLock);
252 :
253 : /* note this assert is okay with newSpace == NULL */
254 : Assert(newSpace == (void *) CACHELINEALIGN(newSpace));
255 :
256 1098170 : return newSpace;
257 : }
258 :
259 : /*
260 : * ShmemAddrIsValid -- test if an address refers to shared memory
261 : *
262 : * Returns true if the pointer points within the shared memory segment.
263 : */
264 : bool
265 0 : ShmemAddrIsValid(const void *addr)
266 : {
267 0 : return (addr >= ShmemBase) && (addr < ShmemEnd);
268 : }
269 :
270 : /*
271 : * InitShmemIndex() --- set up or attach to shmem index table.
272 : */
273 : void
274 2280 : InitShmemIndex(void)
275 : {
276 : HASHCTL info;
277 :
278 : /*
279 : * Create the shared memory shmem index.
280 : *
281 : * Since ShmemInitHash calls ShmemInitStruct, which expects the ShmemIndex
282 : * hashtable to exist already, we have a bit of a circularity problem in
283 : * initializing the ShmemIndex itself. The special "ShmemIndex" hash
284 : * table name will tell ShmemInitStruct to fake it.
285 : */
286 2280 : info.keysize = SHMEM_INDEX_KEYSIZE;
287 2280 : info.entrysize = sizeof(ShmemIndexEnt);
288 :
289 2280 : ShmemIndex = ShmemInitHash("ShmemIndex",
290 : SHMEM_INDEX_SIZE, SHMEM_INDEX_SIZE,
291 : &info,
292 : HASH_ELEM | HASH_STRINGS);
293 2280 : }
294 :
295 : /*
296 : * ShmemInitHash -- Create and initialize, or attach to, a
297 : * shared memory hash table.
298 : *
299 : * We assume caller is doing some kind of synchronization
300 : * so that two processes don't try to create/initialize the same
301 : * table at once. (In practice, all creations are done in the postmaster
302 : * process; child processes should always be attaching to existing tables.)
303 : *
304 : * max_size is the estimated maximum number of hashtable entries. This is
305 : * not a hard limit, but the access efficiency will degrade if it is
306 : * exceeded substantially (since it's used to compute directory size and
307 : * the hash table buckets will get overfull).
308 : *
309 : * init_size is the number of hashtable entries to preallocate. For a table
310 : * whose maximum size is certain, this should be equal to max_size; that
311 : * ensures that no run-time out-of-shared-memory failures can occur.
312 : *
313 : * *infoP and hash_flags must specify at least the entry sizes and key
314 : * comparison semantics (see hash_create()). Flag bits and values specific
315 : * to shared-memory hash tables are added here, except that callers may
316 : * choose to specify HASH_PARTITION and/or HASH_FIXED_SIZE.
317 : *
318 : * Note: before Postgres 9.0, this function returned NULL for some failure
319 : * cases. Now, it always throws error instead, so callers need not check
320 : * for NULL.
321 : */
322 : HTAB *
323 20534 : ShmemInitHash(const char *name, /* table string name for shmem index */
324 : int64 init_size, /* initial table size */
325 : int64 max_size, /* max size of the table */
326 : HASHCTL *infoP, /* info about key and bucket size */
327 : int hash_flags) /* info about infoP */
328 : {
329 : bool found;
330 : void *location;
331 :
332 : /*
333 : * Hash tables allocated in shared memory have a fixed directory; it can't
334 : * grow or other backends wouldn't be able to find it. So, make sure we
335 : * make it big enough to start with.
336 : *
337 : * The shared memory allocator must be specified too.
338 : */
339 20534 : infoP->dsize = infoP->max_dsize = hash_select_dirsize(max_size);
340 20534 : infoP->alloc = ShmemAllocNoError;
341 20534 : hash_flags |= HASH_SHARED_MEM | HASH_ALLOC | HASH_DIRSIZE;
342 :
343 : /* look it up in the shmem index */
344 20534 : location = ShmemInitStruct(name,
345 : hash_get_shared_size(infoP, hash_flags),
346 : &found);
347 :
348 : /*
349 : * if it already exists, attach to it rather than allocate and initialize
350 : * new space
351 : */
352 20534 : if (found)
353 0 : hash_flags |= HASH_ATTACH;
354 :
355 : /* Pass location of hashtable header to hash_create */
356 20534 : infoP->hctl = (HASHHDR *) location;
357 :
358 20534 : return hash_create(name, init_size, infoP, hash_flags);
359 : }
360 :
361 : /*
362 : * ShmemInitStruct -- Create/attach to a structure in shared memory.
363 : *
364 : * This is called during initialization to find or allocate
365 : * a data structure in shared memory. If no other process
366 : * has created the structure, this routine allocates space
367 : * for it. If it exists already, a pointer to the existing
368 : * structure is returned.
369 : *
370 : * Returns: pointer to the object. *foundPtr is set true if the object was
371 : * already in the shmem index (hence, already initialized).
372 : *
373 : * Note: before Postgres 9.0, this function returned NULL for some failure
374 : * cases. Now, it always throws error instead, so callers need not check
375 : * for NULL.
376 : */
377 : void *
378 173278 : ShmemInitStruct(const char *name, Size size, bool *foundPtr)
379 : {
380 : ShmemIndexEnt *result;
381 : void *structPtr;
382 :
383 173278 : LWLockAcquire(ShmemIndexLock, LW_EXCLUSIVE);
384 :
385 173278 : if (!ShmemIndex)
386 : {
387 : /* Must be trying to create/attach to ShmemIndex itself */
388 : Assert(strcmp(name, "ShmemIndex") == 0);
389 :
390 2280 : if (IsUnderPostmaster)
391 : {
392 : /* Must be initializing a (non-standalone) backend */
393 : Assert(ShmemAllocator->index != NULL);
394 0 : structPtr = ShmemAllocator->index;
395 0 : *foundPtr = true;
396 : }
397 : else
398 : {
399 : /*
400 : * If the shmem index doesn't exist, we are bootstrapping: we must
401 : * be trying to init the shmem index itself.
402 : *
403 : * Notice that the ShmemIndexLock is released before the shmem
404 : * index has been initialized. This should be OK because no other
405 : * process can be accessing shared memory yet.
406 : */
407 : Assert(ShmemAllocator->index == NULL);
408 2280 : structPtr = ShmemAlloc(size);
409 2280 : ShmemAllocator->index = structPtr;
410 2280 : *foundPtr = false;
411 : }
412 2280 : LWLockRelease(ShmemIndexLock);
413 2280 : return structPtr;
414 : }
415 :
416 : /* look it up in the shmem index */
417 : result = (ShmemIndexEnt *)
418 170998 : hash_search(ShmemIndex, name, HASH_ENTER_NULL, foundPtr);
419 :
420 170998 : if (!result)
421 : {
422 0 : LWLockRelease(ShmemIndexLock);
423 0 : ereport(ERROR,
424 : (errcode(ERRCODE_OUT_OF_MEMORY),
425 : errmsg("could not create ShmemIndex entry for data structure \"%s\"",
426 : name)));
427 : }
428 :
429 170998 : if (*foundPtr)
430 : {
431 : /*
432 : * Structure is in the shmem index so someone else has allocated it
433 : * already. The size better be the same as the size we are trying to
434 : * initialize to, or there is a name conflict (or worse).
435 : */
436 0 : if (result->size != size)
437 : {
438 0 : LWLockRelease(ShmemIndexLock);
439 0 : ereport(ERROR,
440 : (errmsg("ShmemIndex entry size is wrong for data structure"
441 : " \"%s\": expected %zu, actual %zu",
442 : name, size, result->size)));
443 : }
444 0 : structPtr = result->location;
445 : }
446 : else
447 : {
448 : Size allocated_size;
449 :
450 : /* It isn't in the table yet. allocate and initialize it */
451 170998 : structPtr = ShmemAllocRaw(size, &allocated_size);
452 170998 : if (structPtr == NULL)
453 : {
454 : /* out of memory; remove the failed ShmemIndex entry */
455 0 : hash_search(ShmemIndex, name, HASH_REMOVE, NULL);
456 0 : LWLockRelease(ShmemIndexLock);
457 0 : ereport(ERROR,
458 : (errcode(ERRCODE_OUT_OF_MEMORY),
459 : errmsg("not enough shared memory for data structure"
460 : " \"%s\" (%zu bytes requested)",
461 : name, size)));
462 : }
463 170998 : result->size = size;
464 170998 : result->allocated_size = allocated_size;
465 170998 : result->location = structPtr;
466 : }
467 :
468 170998 : LWLockRelease(ShmemIndexLock);
469 :
470 : Assert(ShmemAddrIsValid(structPtr));
471 :
472 : Assert(structPtr == (void *) CACHELINEALIGN(structPtr));
473 :
474 170998 : return structPtr;
475 : }
476 :
477 :
478 : /*
479 : * Add two Size values, checking for overflow
480 : */
481 : Size
482 1139824 : add_size(Size s1, Size s2)
483 : {
484 : Size result;
485 :
486 1139824 : if (pg_add_size_overflow(s1, s2, &result))
487 0 : ereport(ERROR,
488 : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
489 : errmsg("requested shared memory size overflows size_t")));
490 1139824 : return result;
491 : }
492 :
493 : /*
494 : * Multiply two Size values, checking for overflow
495 : */
496 : Size
497 534232 : mul_size(Size s1, Size s2)
498 : {
499 : Size result;
500 :
501 534232 : if (pg_mul_size_overflow(s1, s2, &result))
502 0 : ereport(ERROR,
503 : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
504 : errmsg("requested shared memory size overflows size_t")));
505 534232 : return result;
506 : }
507 :
508 : /* SQL SRF showing allocated shared memory */
509 : Datum
510 6 : pg_get_shmem_allocations(PG_FUNCTION_ARGS)
511 : {
512 : #define PG_GET_SHMEM_SIZES_COLS 4
513 6 : ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
514 : HASH_SEQ_STATUS hstat;
515 : ShmemIndexEnt *ent;
516 6 : Size named_allocated = 0;
517 : Datum values[PG_GET_SHMEM_SIZES_COLS];
518 : bool nulls[PG_GET_SHMEM_SIZES_COLS];
519 :
520 6 : InitMaterializedSRF(fcinfo, 0);
521 :
522 6 : LWLockAcquire(ShmemIndexLock, LW_SHARED);
523 :
524 6 : hash_seq_init(&hstat, ShmemIndex);
525 :
526 : /* output all allocated entries */
527 6 : memset(nulls, 0, sizeof(nulls));
528 460 : while ((ent = (ShmemIndexEnt *) hash_seq_search(&hstat)) != NULL)
529 : {
530 454 : values[0] = CStringGetTextDatum(ent->key);
531 454 : values[1] = Int64GetDatum((char *) ent->location - (char *) ShmemSegHdr);
532 454 : values[2] = Int64GetDatum(ent->size);
533 454 : values[3] = Int64GetDatum(ent->allocated_size);
534 454 : named_allocated += ent->allocated_size;
535 :
536 454 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
537 : values, nulls);
538 : }
539 :
540 : /* output shared memory allocated but not counted via the shmem index */
541 6 : values[0] = CStringGetTextDatum("<anonymous>");
542 6 : nulls[1] = true;
543 6 : values[2] = Int64GetDatum(ShmemAllocator->free_offset - named_allocated);
544 6 : values[3] = values[2];
545 6 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
546 :
547 : /* output as-of-yet unused shared memory */
548 6 : nulls[0] = true;
549 6 : values[1] = Int64GetDatum(ShmemAllocator->free_offset);
550 6 : nulls[1] = false;
551 6 : values[2] = Int64GetDatum(ShmemSegHdr->totalsize - ShmemAllocator->free_offset);
552 6 : values[3] = values[2];
553 6 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
554 :
555 6 : LWLockRelease(ShmemIndexLock);
556 :
557 6 : return (Datum) 0;
558 : }
559 :
560 : /*
561 : * SQL SRF showing NUMA memory nodes for allocated shared memory
562 : *
563 : * Compared to pg_get_shmem_allocations(), this function does not return
564 : * information about shared anonymous allocations and unused shared memory.
565 : */
566 : Datum
567 6 : pg_get_shmem_allocations_numa(PG_FUNCTION_ARGS)
568 : {
569 : #define PG_GET_SHMEM_NUMA_SIZES_COLS 3
570 6 : ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
571 : HASH_SEQ_STATUS hstat;
572 : ShmemIndexEnt *ent;
573 : Datum values[PG_GET_SHMEM_NUMA_SIZES_COLS];
574 : bool nulls[PG_GET_SHMEM_NUMA_SIZES_COLS];
575 : Size os_page_size;
576 : void **page_ptrs;
577 : int *pages_status;
578 : uint64 shm_total_page_count,
579 : shm_ent_page_count,
580 : max_nodes;
581 : Size *nodes;
582 :
583 6 : if (pg_numa_init() == -1)
584 6 : elog(ERROR, "libnuma initialization failed or NUMA is not supported on this platform");
585 :
586 0 : InitMaterializedSRF(fcinfo, 0);
587 :
588 0 : max_nodes = pg_numa_get_max_node();
589 0 : nodes = palloc_array(Size, max_nodes + 2);
590 :
591 : /*
592 : * Shared memory allocations can vary in size and may not align with OS
593 : * memory page boundaries, while NUMA queries work on pages.
594 : *
595 : * To correctly map each allocation to NUMA nodes, we need to: 1.
596 : * Determine the OS memory page size. 2. Align each allocation's start/end
597 : * addresses to page boundaries. 3. Query NUMA node information for all
598 : * pages spanning the allocation.
599 : */
600 0 : os_page_size = pg_get_shmem_pagesize();
601 :
602 : /*
603 : * Allocate memory for page pointers and status based on total shared
604 : * memory size. This simplified approach allocates enough space for all
605 : * pages in shared memory rather than calculating the exact requirements
606 : * for each segment.
607 : *
608 : * Add 1, because we don't know how exactly the segments align to OS
609 : * pages, so the allocation might use one more memory page. In practice
610 : * this is not very likely, and moreover we have more entries, each of
611 : * them using only fraction of the total pages.
612 : */
613 0 : shm_total_page_count = (ShmemSegHdr->totalsize / os_page_size) + 1;
614 0 : page_ptrs = palloc0_array(void *, shm_total_page_count);
615 0 : pages_status = palloc_array(int, shm_total_page_count);
616 :
617 0 : if (firstNumaTouch)
618 0 : elog(DEBUG1, "NUMA: page-faulting shared memory segments for proper NUMA readouts");
619 :
620 0 : LWLockAcquire(ShmemIndexLock, LW_SHARED);
621 :
622 0 : hash_seq_init(&hstat, ShmemIndex);
623 :
624 : /* output all allocated entries */
625 0 : while ((ent = (ShmemIndexEnt *) hash_seq_search(&hstat)) != NULL)
626 : {
627 : int i;
628 : char *startptr,
629 : *endptr;
630 : Size total_len;
631 :
632 : /*
633 : * Calculate the range of OS pages used by this segment. The segment
634 : * may start / end half-way through a page, we want to count these
635 : * pages too. So we align the start/end pointers down/up, and then
636 : * calculate the number of pages from that.
637 : */
638 0 : startptr = (char *) TYPEALIGN_DOWN(os_page_size, ent->location);
639 0 : endptr = (char *) TYPEALIGN(os_page_size,
640 : (char *) ent->location + ent->allocated_size);
641 0 : total_len = (endptr - startptr);
642 :
643 0 : shm_ent_page_count = total_len / os_page_size;
644 :
645 : /*
646 : * If we ever get 0xff (-1) back from kernel inquiry, then we probably
647 : * have a bug in mapping buffers to OS pages.
648 : */
649 0 : memset(pages_status, 0xff, sizeof(int) * shm_ent_page_count);
650 :
651 : /*
652 : * Setup page_ptrs[] with pointers to all OS pages for this segment,
653 : * and get the NUMA status using pg_numa_query_pages.
654 : *
655 : * In order to get reliable results we also need to touch memory
656 : * pages, so that inquiry about NUMA memory node doesn't return -2
657 : * (ENOENT, which indicates unmapped/unallocated pages).
658 : */
659 0 : for (i = 0; i < shm_ent_page_count; i++)
660 : {
661 0 : page_ptrs[i] = startptr + (i * os_page_size);
662 :
663 0 : if (firstNumaTouch)
664 : pg_numa_touch_mem_if_required(page_ptrs[i]);
665 :
666 0 : CHECK_FOR_INTERRUPTS();
667 : }
668 :
669 0 : if (pg_numa_query_pages(0, shm_ent_page_count, page_ptrs, pages_status) == -1)
670 0 : elog(ERROR, "failed NUMA pages inquiry status: %m");
671 :
672 : /* Count number of NUMA nodes used for this shared memory entry */
673 0 : memset(nodes, 0, sizeof(Size) * (max_nodes + 2));
674 :
675 0 : for (i = 0; i < shm_ent_page_count; i++)
676 : {
677 0 : int s = pages_status[i];
678 :
679 : /* Ensure we are adding only valid index to the array */
680 0 : if (s >= 0 && s <= max_nodes)
681 : {
682 : /* valid NUMA node */
683 0 : nodes[s]++;
684 0 : continue;
685 : }
686 0 : else if (s == -2)
687 : {
688 : /* -2 means ENOENT (e.g. page was moved to swap) */
689 0 : nodes[max_nodes + 1]++;
690 0 : continue;
691 : }
692 :
693 0 : elog(ERROR, "invalid NUMA node id outside of allowed range "
694 : "[0, " UINT64_FORMAT "]: %d", max_nodes, s);
695 : }
696 :
697 : /* no NULLs for regular nodes */
698 0 : memset(nulls, 0, sizeof(nulls));
699 :
700 : /*
701 : * Add one entry for each NUMA node, including those without allocated
702 : * memory for this segment.
703 : */
704 0 : for (i = 0; i <= max_nodes; i++)
705 : {
706 0 : values[0] = CStringGetTextDatum(ent->key);
707 0 : values[1] = Int32GetDatum(i);
708 0 : values[2] = Int64GetDatum(nodes[i] * os_page_size);
709 :
710 0 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
711 : values, nulls);
712 : }
713 :
714 : /* The last entry is used for pages without a NUMA node. */
715 0 : nulls[1] = true;
716 0 : values[0] = CStringGetTextDatum(ent->key);
717 0 : values[2] = Int64GetDatum(nodes[max_nodes + 1] * os_page_size);
718 :
719 0 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
720 : values, nulls);
721 : }
722 :
723 0 : LWLockRelease(ShmemIndexLock);
724 0 : firstNumaTouch = false;
725 :
726 0 : return (Datum) 0;
727 : }
728 :
729 : /*
730 : * Determine the memory page size used for the shared memory segment.
731 : *
732 : * If the shared segment was allocated using huge pages, returns the size of
733 : * a huge page. Otherwise returns the size of regular memory page.
734 : *
735 : * This should be used only after the server is started.
736 : */
737 : Size
738 4 : pg_get_shmem_pagesize(void)
739 : {
740 : Size os_page_size;
741 : #ifdef WIN32
742 : SYSTEM_INFO sysinfo;
743 :
744 : GetSystemInfo(&sysinfo);
745 : os_page_size = sysinfo.dwPageSize;
746 : #else
747 4 : os_page_size = sysconf(_SC_PAGESIZE);
748 : #endif
749 :
750 : Assert(IsUnderPostmaster);
751 : Assert(huge_pages_status != HUGE_PAGES_UNKNOWN);
752 :
753 4 : if (huge_pages_status == HUGE_PAGES_ON)
754 0 : GetHugePageSize(&os_page_size, NULL);
755 :
756 4 : return os_page_size;
757 : }
758 :
759 : Datum
760 8 : pg_numa_available(PG_FUNCTION_ARGS)
761 : {
762 8 : PG_RETURN_BOOL(pg_numa_init() != -1);
763 : }
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