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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 : : * This module provides facilities to allocate fixed-size structures in shared
23 : : * memory, for things like variables shared between all backend processes.
24 : : * Each such structure has a string name to identify it, specified when it is
25 : : * requested. shmem_hash.c provides a shared hash table implementation on top
26 : : * of that.
27 : : *
28 : : * Shared memory areas should usually not be allocated after postmaster
29 : : * startup, although we do allow small allocations later for the benefit of
30 : : * extension modules that are loaded after startup. Despite that allowance,
31 : : * extensions that need shared memory should be added in
32 : : * shared_preload_libraries, because the allowance is quite small and there is
33 : : * no guarantee that any memory is available after startup.
34 : : *
35 : : * Nowadays, there is also another way to allocate shared memory called
36 : : * Dynamic Shared Memory. See dsm.c for that facility. One big difference
37 : : * between traditional shared memory handled by shmem.c and dynamic shared
38 : : * memory is that traditional shared memory areas are mapped to the same
39 : : * address in all processes, so you can use normal pointers in shared memory
40 : : * structs. With Dynamic Shared Memory, you must use offsets or DSA pointers
41 : : * instead.
42 : : *
43 : : * Shared memory managed by shmem.c can never be freed, once allocated. Each
44 : : * hash table has its own free list, so hash buckets can be reused when an
45 : : * item is deleted.
46 : : *
47 : : * Usage
48 : : * -----
49 : : *
50 : : * To allocate shared memory, you need to register a set of callback functions
51 : : * which handle the lifecycle of the allocation. In the request_fn callback,
52 : : * call ShmemRequestStruct() with the desired name and size. When the area is
53 : : * later allocated or attached to, the global variable pointed to by the .ptr
54 : : * option is set to the shared memory location of the allocation. The init_fn
55 : : * callback can perform additional initialization.
56 : : *
57 : : * typedef struct MyShmemData {
58 : : * ...
59 : : * } MyShmemData;
60 : : *
61 : : * static MyShmemData *MyShmem;
62 : : *
63 : : * static void my_shmem_request(void *arg);
64 : : * static void my_shmem_init(void *arg);
65 : : *
66 : : * const ShmemCallbacks MyShmemCallbacks = {
67 : : * .request_fn = my_shmem_request,
68 : : * .init_fn = my_shmem_init,
69 : : * };
70 : : *
71 : : * static void
72 : : * my_shmem_request(void *arg)
73 : : * {
74 : : * ShmemRequestStruct(.name = "My shmem area",
75 : : * .size = sizeof(MyShmemData),
76 : : * .ptr = (void **) &MyShmem,
77 : : * );
78 : : * }
79 : : *
80 : : * In builtin PostgreSQL code, add the callbacks to the list in
81 : : * src/include/storage/subsystemlist.h. In an add-in module, you can register
82 : : * the callbacks by calling RegisterShmemCallbacks(&MyShmemCallbacks) in the
83 : : * extension's _PG_init() function.
84 : : *
85 : : * Lifecycle
86 : : * ---------
87 : : *
88 : : * Initializing shared memory happens in multiple phases. In the first phase,
89 : : * during postmaster startup, all the request_fn callbacks are called. Only
90 : : * after all the request_fn callbacks have been called and all the shmem areas
91 : : * have been requested by the ShmemRequestStruct() calls we know how much
92 : : * shared memory we need in total. After that, postmaster allocates global
93 : : * shared memory segment, and calls all the init_fn callbacks to initialize
94 : : * all the requested shmem areas.
95 : : *
96 : : * In standard Unix-ish environments, individual backends do not need to
97 : : * re-establish their local pointers into shared memory, because they inherit
98 : : * correct values of those variables via fork() from the postmaster. However,
99 : : * this does not work in the EXEC_BACKEND case. In ports using EXEC_BACKEND,
100 : : * backend startup also calls the shmem_request callbacks to re-establish the
101 : : * knowledge about each shared memory area, sets the pointer variables
102 : : * (*options->ptr), and calls the attach_fn callback, if any, for additional
103 : : * per-backend setup.
104 : : *
105 : : * Legacy ShmemInitStruct()/ShmemInitHash() functions
106 : : * --------------------------------------------------
107 : : *
108 : : * ShmemInitStruct()/ShmemInitHash() is another way of registering shmem
109 : : * areas. It pre-dates the ShmemRequestStruct()/ShmemRequestHash() functions,
110 : : * and should not be used in new code, but as of this writing it is still
111 : : * widely used in extensions.
112 : : *
113 : : * To allocate a shmem area with ShmemInitStruct(), you need to separately
114 : : * register the size needed for the area by calling RequestAddinShmemSpace()
115 : : * from the extension's shmem_request_hook, and allocate the area by calling
116 : : * ShmemInitStruct() from the extension's shmem_startup_hook. There are no
117 : : * init/attach callbacks. Instead, the caller of ShmemInitStruct() must check
118 : : * the return status of ShmemInitStruct() and initialize the struct if it was
119 : : * not previously initialized.
120 : : *
121 : : * Calling ShmemAlloc() directly
122 : : * -----------------------------
123 : : *
124 : : * There's a more low-level way of allocating shared memory too: you can call
125 : : * ShmemAlloc() directly. It's used to implement the higher level mechanisms,
126 : : * and should generally not be called directly.
127 : : */
128 : :
129 : : #include "postgres.h"
130 : :
131 : : #include <unistd.h>
132 : :
133 : : #include "access/slru.h"
134 : : #include "fmgr.h"
135 : : #include "funcapi.h"
136 : : #include "miscadmin.h"
137 : : #include "port/pg_bitutils.h"
138 : : #include "port/pg_numa.h"
139 : : #include "storage/lwlock.h"
140 : : #include "storage/pg_shmem.h"
141 : : #include "storage/shmem.h"
142 : : #include "storage/shmem_internal.h"
143 : : #include "storage/spin.h"
144 : : #include "utils/builtins.h"
145 : : #include "utils/tuplestore.h"
146 : :
147 : : typedef struct ShmemIndexEnt ShmemIndexEnt;
148 : :
149 : : /*
150 : : * Registered callbacks.
151 : : *
152 : : * During postmaster startup, we accumulate the callbacks from all subsystems
153 : : * in this list.
154 : : *
155 : : * This is in process private memory, although on Unix-like systems, we expect
156 : : * all the registrations to happen at postmaster startup time and be inherited
157 : : * by all the child processes via fork().
158 : : */
159 : : static List *registered_shmem_callbacks;
160 : :
161 : : /*
162 : : * In the shmem request phase, all the shmem areas requested with the
163 : : * ShmemRequest*() functions are accumulated in the 'pending_shmem_requests'
164 : : * list. The List, the ShmemRequest structs, and the 'options' are all
165 : : * allocated in TopMemoryContext.
166 : : */
167 : : typedef struct
168 : : {
169 : : ShmemStructOpts *options;
170 : : ShmemRequestKind kind;
171 : :
172 : : /* InitShmemIndexEntry() sets this pointer when the area is allocated */
173 : : ShmemIndexEnt *index_entry;
174 : : } ShmemRequest;
175 : :
176 : : static List *pending_shmem_requests; /* List of ShmemRequests */
177 : :
178 : : /*
179 : : * Per-process state machine, for sanity checking that we do things in the
180 : : * right order.
181 : : *
182 : : * Postmaster:
183 : : * INITIAL -> REQUESTING -> INITIALIZING -> DONE
184 : : *
185 : : * Backends in EXEC_BACKEND mode:
186 : : * INITIAL -> REQUESTING -> ATTACHING -> DONE
187 : : *
188 : : * Late request:
189 : : * DONE -> REQUESTING -> AFTER_STARTUP_ATTACH_OR_INIT -> DONE
190 : : */
191 : : enum shmem_request_state
192 : : {
193 : : /* Initial state */
194 : : SRS_INITIAL,
195 : :
196 : : /*
197 : : * When we start calling the shmem_request callbacks, we enter the
198 : : * SRS_REQUESTING phase. All ShmemRequestStruct calls happen in this
199 : : * state.
200 : : */
201 : : SRS_REQUESTING,
202 : :
203 : : /*
204 : : * Postmaster has finished all shmem requests, and is now initializing the
205 : : * shared memory segment. init_fn callbacks are called in this state.
206 : : */
207 : : SRS_INITIALIZING,
208 : :
209 : : /*
210 : : * A postmaster child process is starting up. attach_fn callbacks are
211 : : * called in this state.
212 : : */
213 : : SRS_ATTACHING,
214 : :
215 : : /* An after-startup allocation or attachment is in progress */
216 : : SRS_AFTER_STARTUP_ATTACH_OR_INIT,
217 : :
218 : : /* Normal state after shmem initialization / attachment */
219 : : SRS_DONE,
220 : : };
221 : : static enum shmem_request_state shmem_request_state = SRS_INITIAL;
222 : :
223 : : /*
224 : : * This is the first data structure stored in the shared memory segment, at
225 : : * the offset that PGShmemHeader->content_offset points to. Allocations by
226 : : * ShmemAlloc() are carved out of the space after this.
227 : : *
228 : : * For the base pointer and the total size of the shmem segment, we rely on
229 : : * the PGShmemHeader.
230 : : */
231 : : typedef struct ShmemAllocatorData
232 : : {
233 : : Size free_offset; /* offset to first free space from ShmemBase */
234 : :
235 : : /* protects 'free_offset' */
236 : : slock_t shmem_lock;
237 : :
238 : : HASHHDR *index; /* location of ShmemIndex */
239 : : size_t index_size; /* size of shmem region holding ShmemIndex */
240 : : LWLock index_lock; /* protects ShmemIndex */
241 : : } ShmemAllocatorData;
242 : :
243 : : #define ShmemIndexLock (&ShmemAllocator->index_lock)
244 : :
245 : : static void *ShmemAllocRaw(Size size, Size alignment, Size *allocated_size);
246 : :
247 : : /* shared memory global variables */
248 : :
249 : : static PGShmemHeader *ShmemSegHdr; /* shared mem segment header */
250 : : static void *ShmemBase; /* start address of shared memory */
251 : : static void *ShmemEnd; /* end+1 address of shared memory */
252 : :
253 : : static ShmemAllocatorData *ShmemAllocator;
254 : :
255 : : /*
256 : : * ShmemIndex is a global directory of shmem areas, itself also stored in the
257 : : * shared memory.
258 : : */
259 : : static HTAB *ShmemIndex;
260 : :
261 : : /* max size of data structure string name */
262 : : #define SHMEM_INDEX_KEYSIZE (48)
263 : :
264 : : /*
265 : : * # of additional entries to reserve in the shmem index table, for
266 : : * allocations after postmaster startup. (This is not a hard limit, the hash
267 : : * table can grow larger than that if there is shared memory available)
268 : : */
269 : : #define SHMEM_INDEX_ADDITIONAL_SIZE (128)
270 : :
271 : : /* this is a hash bucket in the shmem index table */
272 : : typedef struct ShmemIndexEnt
273 : : {
274 : : char key[SHMEM_INDEX_KEYSIZE]; /* string name */
275 : : void *location; /* location in shared mem */
276 : : Size size; /* # bytes requested for the structure */
277 : : Size allocated_size; /* # bytes actually allocated */
278 : : bool initialized; /* has the init callback been run? */
279 : : } ShmemIndexEnt;
280 : :
281 : : /* To get reliable results for NUMA inquiry we need to "touch pages" once */
282 : : static bool firstNumaTouch = true;
283 : :
284 : : static void CallShmemCallbacksAfterStartup(const ShmemCallbacks *callbacks);
285 : : static void ProcessShmemRequestsAfterStartup(const ShmemCallbacks *callbacks);
286 : : static void InitShmemIndexEntry(ShmemRequest *request);
287 : : static bool AttachShmemIndexEntry(ShmemRequest *request, bool missing_ok);
288 : :
289 : : Datum pg_numa_available(PG_FUNCTION_ARGS);
290 : :
291 : : /*
292 : : * ShmemRequestStruct() --- request a named shared memory area
293 : : *
294 : : * Subsystems call this to register their shared memory needs. This is
295 : : * usually done early in postmaster startup, before the shared memory segment
296 : : * has been created, so that the size can be included in the estimate for
297 : : * total amount of shared memory needed. We set aside a small amount of
298 : : * memory for allocations that happen later, for the benefit of non-preloaded
299 : : * extensions, but that should not be relied upon.
300 : : *
301 : : * This does not yet allocate the memory, but merely registers the need for
302 : : * it. The actual allocation happens later in the postmaster startup
303 : : * sequence.
304 : : *
305 : : * This must be called from a shmem_request callback function, registered with
306 : : * RegisterShmemCallbacks(). This enforces a coding pattern that works the
307 : : * same in normal Unix systems and with EXEC_BACKEND. On Unix systems, the
308 : : * shmem_request callbacks are called once, early in postmaster startup, and
309 : : * the child processes inherit the struct descriptors and any other
310 : : * per-process state from the postmaster. In EXEC_BACKEND mode, shmem_request
311 : : * callbacks are *also* called in each backend, at backend startup, to
312 : : * re-establish the struct descriptors. By calling the same function in both
313 : : * cases, we ensure that all the shmem areas are registered the same way in
314 : : * all processes.
315 : : *
316 : : * 'options' defines the name and size of the area, and any other optional
317 : : * features. Leave unused options as zeros. The options are copied to
318 : : * longer-lived memory, so it doesn't need to live after the
319 : : * ShmemRequestStruct() call and can point to a local variable in the calling
320 : : * function. The 'name' must point to a long-lived string though, only the
321 : : * pointer to it is copied.
322 : : */
323 : : void
324 : 80643 : ShmemRequestStructWithOpts(const ShmemStructOpts *options)
325 : : {
326 : : ShmemStructOpts *options_copy;
327 : :
328 : 80643 : options_copy = MemoryContextAlloc(TopMemoryContext,
329 : : sizeof(ShmemStructOpts));
330 : 80643 : memcpy(options_copy, options, sizeof(ShmemStructOpts));
331 : :
332 : 80643 : ShmemRequestInternal(options_copy, SHMEM_KIND_STRUCT);
333 : 80643 : }
334 : :
335 : : /*
336 : : * Internal workhorse of ShmemRequestStruct() and ShmemRequestHash().
337 : : *
338 : : * Note: Unlike in the public ShmemRequestStruct() and ShmemRequestHash()
339 : : * functions, 'options' is *not* copied. It must be allocated in
340 : : * TopMemoryContext by the caller, and will be freed after the init/attach
341 : : * callbacks have been called. This allows ShmemRequestHash() to pass a
342 : : * pointer to the extended ShmemHashOpts struct instead.
343 : : */
344 : : void
345 : 99858 : ShmemRequestInternal(ShmemStructOpts *options, ShmemRequestKind kind)
346 : : {
347 : : MemoryContext oldcontext;
348 : : ShmemRequest *request;
349 : :
350 : : /* Check the options */
351 [ - + ]: 99858 : if (options->name == NULL)
352 [ # # ]: 0 : elog(ERROR, "shared memory request is missing 'name' option");
353 : :
354 [ + + ]: 99858 : if (IsUnderPostmaster)
355 : : {
356 [ - + - - ]: 7 : if (options->size <= 0 && options->size != SHMEM_ATTACH_UNKNOWN_SIZE)
357 [ # # ]: 0 : elog(ERROR, "invalid size %zd for shared memory request for \"%s\"",
358 : : options->size, options->name);
359 : : }
360 : : else
361 : : {
362 [ - + ]: 99851 : if (options->size == SHMEM_ATTACH_UNKNOWN_SIZE)
363 [ # # ]: 0 : elog(ERROR, "SHMEM_ATTACH_UNKNOWN_SIZE cannot be used during startup");
364 [ - + ]: 99851 : if (options->size <= 0)
365 [ # # ]: 0 : elog(ERROR, "invalid size %zd for shared memory request for \"%s\"",
366 : : options->size, options->name);
367 : : }
368 : :
369 [ + + - + ]: 99858 : if (options->alignment != 0 && pg_nextpower2_size_t(options->alignment) != options->alignment)
370 [ # # ]: 0 : elog(ERROR, "invalid alignment %zu for shared memory request for \"%s\"",
371 : : options->alignment, options->name);
372 : :
373 : : /* Check that we're in the right state */
374 [ - + ]: 99858 : if (shmem_request_state != SRS_REQUESTING)
375 [ # # ]: 0 : elog(ERROR, "ShmemRequestStruct can only be called from a shmem_request callback");
376 : :
377 : : /* Check that it's not already registered in this process */
378 [ + + + + : 4044383 : foreach_ptr(ShmemRequest, existing, pending_shmem_requests)
+ + ]
379 : : {
380 [ - + ]: 3844667 : if (strcmp(existing->options->name, options->name) == 0)
381 [ # # ]: 0 : ereport(ERROR,
382 : : (errmsg("shared memory struct \"%s\" is already registered",
383 : : options->name)));
384 : : }
385 : :
386 : : /* Request looks valid, remember it */
387 : 99858 : oldcontext = MemoryContextSwitchTo(TopMemoryContext);
388 : 99858 : request = palloc_object(ShmemRequest);
389 : 99858 : request->options = options;
390 : 99858 : request->kind = kind;
391 : 99858 : request->index_entry = NULL;
392 : 99858 : pending_shmem_requests = lappend(pending_shmem_requests, request);
393 : 99858 : MemoryContextSwitchTo(oldcontext);
394 : 99858 : }
395 : :
396 : : /*
397 : : * ShmemGetRequestedSize() --- estimate the total size of all registered shared
398 : : * memory structures.
399 : : *
400 : : * This is called at postmaster startup, before the shared memory segment has
401 : : * been created.
402 : : */
403 : : size_t
404 : 2386 : ShmemGetRequestedSize(void)
405 : : {
406 : : size_t size;
407 : :
408 : : /* memory needed for the ShmemIndex */
409 : 2386 : size = hash_estimate_size(list_length(pending_shmem_requests) + SHMEM_INDEX_ADDITIONAL_SIZE,
410 : : sizeof(ShmemIndexEnt));
411 : 2386 : size = CACHELINEALIGN(size);
412 : :
413 : : /* memory needed for all the requested areas */
414 [ + - + + : 190902 : foreach_ptr(ShmemRequest, request, pending_shmem_requests)
+ + ]
415 : : {
416 : 186130 : size_t alignment = request->options->alignment;
417 : :
418 : : /* pad the start address for alignment like ShmemAllocRaw() does */
419 [ + + ]: 186130 : if (alignment < PG_CACHE_LINE_SIZE)
420 : 178972 : alignment = PG_CACHE_LINE_SIZE;
421 : 186130 : size = TYPEALIGN(alignment, size);
422 : :
423 : 186130 : size = add_size(size, request->options->size);
424 : : }
425 : :
426 : 2386 : return size;
427 : : }
428 : :
429 : : /*
430 : : * ShmemInitRequested() --- allocate and initialize requested shared memory
431 : : * structures.
432 : : *
433 : : * This is called once at postmaster startup, after the shared memory segment
434 : : * has been created.
435 : : */
436 : : void
437 : 1277 : ShmemInitRequested(void)
438 : : {
439 : : /* should be called only by the postmaster or a standalone backend */
440 : : Assert(!IsUnderPostmaster);
441 : : Assert(shmem_request_state == SRS_INITIALIZING);
442 : :
443 : : /*
444 : : * Initialize the ShmemIndex entries and perform basic initialization of
445 : : * all the requested memory areas. There are no concurrent processes yet,
446 : : * so no need for locking.
447 : : */
448 [ + - + + : 102170 : foreach_ptr(ShmemRequest, request, pending_shmem_requests)
+ + ]
449 : : {
450 : 99616 : InitShmemIndexEntry(request);
451 : : }
452 : :
453 : : /*
454 : : * Call the subsystem-specific init callbacks to finish initialization of
455 : : * all the areas.
456 : : */
457 [ + - + + : 58768 : foreach_ptr(const ShmemCallbacks, callbacks, registered_shmem_callbacks)
+ + ]
458 : : {
459 [ + + ]: 56214 : if (callbacks->init_fn)
460 : 51102 : callbacks->init_fn(callbacks->opaque_arg);
461 : : }
462 : :
463 : : /* Now we can mark all the areas as initialized and free the requests */
464 [ + - + + : 102170 : foreach_ptr(ShmemRequest, request, pending_shmem_requests)
+ + ]
465 : : {
466 : 99616 : request->index_entry->initialized = true;
467 : 99616 : pfree(request->options);
468 : : }
469 : 1277 : list_free_deep(pending_shmem_requests);
470 : 1277 : pending_shmem_requests = NIL;
471 : :
472 : 1277 : shmem_request_state = SRS_DONE;
473 : 1277 : }
474 : :
475 : : /*
476 : : * Re-establish process private state related to shmem areas.
477 : : *
478 : : * This is called at backend startup in EXEC_BACKEND mode, in every backend.
479 : : */
480 : : #ifdef EXEC_BACKEND
481 : : void
482 : : ShmemAttachRequested(void)
483 : : {
484 : : ListCell *lc;
485 : :
486 : : /* Must be initializing a (non-standalone) backend */
487 : : Assert(IsUnderPostmaster);
488 : : Assert(ShmemAllocator->index != NULL);
489 : : Assert(shmem_request_state == SRS_REQUESTING);
490 : : shmem_request_state = SRS_ATTACHING;
491 : :
492 : : LWLockAcquire(ShmemIndexLock, LW_SHARED);
493 : :
494 : : /*
495 : : * Attach to all the requested memory areas.
496 : : */
497 : : foreach_ptr(ShmemRequest, request, pending_shmem_requests)
498 : : {
499 : : AttachShmemIndexEntry(request, false);
500 : : pfree(request->options);
501 : : }
502 : : list_free_deep(pending_shmem_requests);
503 : : pending_shmem_requests = NIL;
504 : :
505 : : /* Call attach callbacks */
506 : : foreach(lc, registered_shmem_callbacks)
507 : : {
508 : : const ShmemCallbacks *callbacks = (const ShmemCallbacks *) lfirst(lc);
509 : :
510 : : if (callbacks->attach_fn)
511 : : callbacks->attach_fn(callbacks->opaque_arg);
512 : : }
513 : :
514 : : LWLockRelease(ShmemIndexLock);
515 : :
516 : : shmem_request_state = SRS_DONE;
517 : : }
518 : : #endif
519 : :
520 : : /*
521 : : * Insert requested shmem area into the shared memory index and initialize it.
522 : : *
523 : : * Note that this only does performs basic initialization depending on
524 : : * ShmemRequestKind, like setting the global pointer variable to the area for
525 : : * SHMEM_KIND_STRUCT or setting up the backend-private HTAB control struct.
526 : : * This does *not* call the subsystem-specific init callbacks. That's done
527 : : * later after all the shmem areas have been initialized or attached to.
528 : : */
529 : : static void
530 : 99622 : InitShmemIndexEntry(ShmemRequest *request)
531 : : {
532 : 99622 : const char *name = request->options->name;
533 : : ShmemIndexEnt *index_entry;
534 : : bool found;
535 : : size_t allocated_size;
536 : : void *structPtr;
537 : :
538 : : /* look it up in the shmem index */
539 : : index_entry = (ShmemIndexEnt *)
540 : 99622 : hash_search(ShmemIndex, name, HASH_ENTER_NULL, &found);
541 [ - + ]: 99622 : if (found)
542 [ # # ]: 0 : elog(ERROR, "shared memory struct \"%s\" is already initialized", name);
543 [ - + ]: 99622 : if (!index_entry)
544 : : {
545 : : /* tried to add it to the hash table, but there was no space */
546 [ # # ]: 0 : ereport(ERROR,
547 : : (errcode(ERRCODE_OUT_OF_MEMORY),
548 : : errmsg("could not create ShmemIndex entry for data structure \"%s\"",
549 : : name)));
550 : : }
551 : :
552 : : /*
553 : : * We inserted the entry to the shared memory index. Allocate requested
554 : : * amount of shared memory for it, and initialize the index entry.
555 : : */
556 : 99622 : structPtr = ShmemAllocRaw(request->options->size,
557 : 99622 : request->options->alignment,
558 : : &allocated_size);
559 [ + + ]: 99622 : if (structPtr == NULL)
560 : : {
561 : : /* out of memory; remove the failed ShmemIndex entry */
562 : 1 : hash_search(ShmemIndex, name, HASH_REMOVE, NULL);
563 [ + - ]: 1 : ereport(ERROR,
564 : : (errcode(ERRCODE_OUT_OF_MEMORY),
565 : : errmsg("not enough shared memory for data structure"
566 : : " \"%s\" (%zd bytes requested)",
567 : : name, request->options->size)));
568 : : }
569 : 99621 : index_entry->size = request->options->size;
570 : 99621 : index_entry->allocated_size = allocated_size;
571 : 99621 : index_entry->location = structPtr;
572 : :
573 : : /*
574 : : * The area is considered fully initialized only after the subsystem's
575 : : * init callback has been called. For now, perform only basic
576 : : * initialization based on the kind of shmem area it is.
577 : : */
578 : 99621 : index_entry->initialized = false;
579 [ + + + - ]: 99621 : switch (request->kind)
580 : : {
581 : 80451 : case SHMEM_KIND_STRUCT:
582 [ + - ]: 80451 : if (request->options->ptr)
583 : 80451 : *(request->options->ptr) = index_entry->location;
584 : 80451 : break;
585 : 10227 : case SHMEM_KIND_HASH:
586 : 10227 : shmem_hash_init(structPtr, request->options);
587 : 10227 : break;
588 : 8943 : case SHMEM_KIND_SLRU:
589 : 8943 : shmem_slru_init(structPtr, request->options);
590 : 8943 : break;
591 : : }
592 : :
593 : : /* return the pointer to the entry to the caller */
594 : 99621 : request->index_entry = index_entry;
595 : 99621 : }
596 : :
597 : : /*
598 : : * Look up a named shmem area in the shared memory index and attach to it.
599 : : *
600 : : * Note that this only performs the basic attachment actions depending on
601 : : * ShmemRequestKind, like setting the global pointer variable to the area for
602 : : * SHMEM_KIND_STRUCT or setting up the backend-private HTAB control struct.
603 : : * This does *not* call the subsystem-specific attach callbacks. That's done
604 : : * later after all the shmem areas have been initialized or attached to.
605 : : */
606 : : static bool
607 : 1 : AttachShmemIndexEntry(ShmemRequest *request, bool missing_ok)
608 : : {
609 : 1 : const char *name = request->options->name;
610 : : ShmemIndexEnt *index_entry;
611 : :
612 : : /* Look it up in the shmem index */
613 : : index_entry = (ShmemIndexEnt *)
614 : 1 : hash_search(ShmemIndex, name, HASH_FIND, NULL);
615 [ - + ]: 1 : if (!index_entry)
616 : : {
617 [ # # ]: 0 : if (!missing_ok)
618 [ # # ]: 0 : ereport(ERROR,
619 : : (errmsg("could not find ShmemIndex entry for data structure \"%s\"",
620 : : request->options->name)));
621 : 0 : return false;
622 : : }
623 : :
624 : : /*
625 : : * If it was previously allocated but not fully initialized, error out.
626 : : * There is currently no way of retrying or cleaning up an uninitialized
627 : : * entry, it just lingers until the server is shut down. But this can
628 : : * only happen when allocating areas after postmaster startup, and it's
629 : : * unlikely that you could successfully retry anyway. The most likely
630 : : * reason for failed initialization is that you are out of shared memory
631 : : * and retrying won't help with that.
632 : : */
633 [ - + ]: 1 : if (!index_entry->initialized)
634 [ # # ]: 0 : ereport(ERROR,
635 : : (errmsg("cannot attach to shared memory struct \"%s\" because it was not fully initialized",
636 : : request->options->name)));
637 : :
638 : : /* Check that the size in the index matches the request */
639 [ - + ]: 1 : if (index_entry->size != request->options->size &&
640 [ # # ]: 0 : request->options->size != SHMEM_ATTACH_UNKNOWN_SIZE)
641 : : {
642 [ # # ]: 0 : ereport(ERROR,
643 : : (errmsg("shared memory struct \"%s\" was created with"
644 : : " different size: existing %zu, requested %zd",
645 : : name, index_entry->size, request->options->size)));
646 : : }
647 : :
648 : : /*
649 : : * Re-establish the caller's pointer variable, or do other actions to
650 : : * attach depending on the kind of shmem area it is.
651 : : */
652 [ + - - - ]: 1 : switch (request->kind)
653 : : {
654 : 1 : case SHMEM_KIND_STRUCT:
655 [ + - ]: 1 : if (request->options->ptr)
656 : 1 : *(request->options->ptr) = index_entry->location;
657 : 1 : break;
658 : 0 : case SHMEM_KIND_HASH:
659 : 0 : shmem_hash_attach(index_entry->location, request->options);
660 : 0 : break;
661 : 0 : case SHMEM_KIND_SLRU:
662 : 0 : shmem_slru_attach(index_entry->location, request->options);
663 : 0 : break;
664 : : }
665 : :
666 : 1 : request->index_entry = index_entry;
667 : :
668 : 1 : return true;
669 : : }
670 : :
671 : : /*
672 : : * InitShmemAllocator() --- set up basic pointers to shared memory.
673 : : *
674 : : * Called at postmaster or stand-alone backend startup, to initialize the
675 : : * allocator's data structure in the shared memory segment. In EXEC_BACKEND,
676 : : * this is also called at backend startup, to set up pointers to the
677 : : * already-initialized data structure.
678 : : */
679 : : void
680 : 1277 : InitShmemAllocator(PGShmemHeader *seghdr)
681 : : {
682 : : Size offset;
683 : : int64 hash_nelems;
684 : : HASHCTL info;
685 : : int hash_flags;
686 : :
687 : : #ifndef EXEC_BACKEND
688 : : Assert(!IsUnderPostmaster);
689 : : #endif
690 : : Assert(seghdr != NULL);
691 : :
692 [ + - ]: 1277 : if (IsUnderPostmaster)
693 : : {
694 : : Assert(shmem_request_state == SRS_INITIAL);
695 : : }
696 : : else
697 : : {
698 : : Assert(shmem_request_state == SRS_REQUESTING);
699 : 1277 : shmem_request_state = SRS_INITIALIZING;
700 : : }
701 : :
702 : : /*
703 : : * We assume the pointer and offset are MAXALIGN. Not a hard requirement,
704 : : * but it's true today and keeps the math below simpler.
705 : : */
706 : : Assert(seghdr == (void *) MAXALIGN(seghdr));
707 : : Assert(seghdr->content_offset == MAXALIGN(seghdr->content_offset));
708 : :
709 : : /*
710 : : * Allocations after this point should go through ShmemAlloc, which
711 : : * expects to allocate everything on cache line boundaries. Make sure the
712 : : * first allocation begins on a cache line boundary.
713 : : */
714 : 1277 : offset = CACHELINEALIGN(seghdr->content_offset + sizeof(ShmemAllocatorData));
715 [ - + ]: 1277 : if (offset > seghdr->totalsize)
716 [ # # ]: 0 : ereport(ERROR,
717 : : (errcode(ERRCODE_OUT_OF_MEMORY),
718 : : errmsg("out of shared memory (%zu bytes requested)",
719 : : offset)));
720 : :
721 : : /*
722 : : * In postmaster or stand-alone backend, initialize the shared memory
723 : : * allocator so that we can allocate shared memory for ShmemIndex using
724 : : * ShmemAlloc(). In a regular backend just set up the pointers required
725 : : * by ShmemAlloc().
726 : : */
727 : 1277 : ShmemAllocator = (ShmemAllocatorData *) ((char *) seghdr + seghdr->content_offset);
728 [ + - ]: 1277 : if (!IsUnderPostmaster)
729 : : {
730 : 1277 : SpinLockInit(&ShmemAllocator->shmem_lock);
731 : 1277 : ShmemAllocator->free_offset = offset;
732 : 1277 : LWLockInitialize(&ShmemAllocator->index_lock, LWTRANCHE_SHMEM_INDEX);
733 : : }
734 : :
735 : 1277 : ShmemSegHdr = seghdr;
736 : 1277 : ShmemBase = seghdr;
737 : 1277 : ShmemEnd = (char *) ShmemBase + seghdr->totalsize;
738 : :
739 : : /*
740 : : * Create (or attach to) the shared memory index of shmem areas.
741 : : *
742 : : * This is the same initialization as ShmemInitHash() does, but we cannot
743 : : * use ShmemInitHash() here because it relies on ShmemIndex being already
744 : : * initialized.
745 : : */
746 : 1277 : hash_nelems = list_length(pending_shmem_requests) + SHMEM_INDEX_ADDITIONAL_SIZE;
747 : :
748 : 1277 : info.keysize = SHMEM_INDEX_KEYSIZE;
749 : 1277 : info.entrysize = sizeof(ShmemIndexEnt);
750 : 1277 : hash_flags = HASH_ELEM | HASH_STRINGS | HASH_FIXED_SIZE;
751 : :
752 [ + - ]: 1277 : if (!IsUnderPostmaster)
753 : : {
754 : 1277 : ShmemAllocator->index_size = hash_estimate_size(hash_nelems, info.entrysize);
755 : 1277 : ShmemAllocator->index = (HASHHDR *) ShmemAlloc(ShmemAllocator->index_size);
756 : : }
757 : 2554 : ShmemIndex = shmem_hash_create(ShmemAllocator->index,
758 : 1277 : ShmemAllocator->index_size,
759 : : IsUnderPostmaster,
760 : : "ShmemIndex", hash_nelems,
761 : : &info, hash_flags);
762 : : Assert(ShmemIndex != NULL);
763 : :
764 : : /*
765 : : * Add an entry for ShmemIndex itself into ShmemIndex, so that it's
766 : : * visible in the pg_shmem_allocations view
767 : : */
768 [ + - ]: 1277 : if (!IsUnderPostmaster)
769 : : {
770 : : bool found;
771 : : ShmemIndexEnt *result = (ShmemIndexEnt *)
772 : 1277 : hash_search(ShmemIndex, "ShmemIndex", HASH_ENTER, &found);
773 : :
774 : : Assert(!found);
775 : 1277 : result->size = ShmemAllocator->index_size;
776 : 1277 : result->allocated_size = ShmemAllocator->index_size;
777 : 1277 : result->location = ShmemAllocator->index;
778 : 1277 : result->initialized = true;
779 : : }
780 : 1277 : }
781 : :
782 : : /*
783 : : * Reset state on postmaster crash restart.
784 : : */
785 : : void
786 : 5 : ResetShmemAllocator(void)
787 : : {
788 : : Assert(!IsUnderPostmaster);
789 : 5 : shmem_request_state = SRS_INITIAL;
790 : :
791 : 5 : pending_shmem_requests = NIL;
792 : :
793 : : /*
794 : : * Note that we don't clear the registered callbacks. We will need to
795 : : * call them again as we restart
796 : : */
797 : 5 : }
798 : :
799 : : /*
800 : : * ShmemAlloc -- allocate max-aligned chunk from shared memory
801 : : *
802 : : * Throws error if request cannot be satisfied.
803 : : *
804 : : * Assumes ShmemSegHdr is initialized.
805 : : */
806 : : void *
807 : 1277 : ShmemAlloc(Size size)
808 : : {
809 : : void *newSpace;
810 : : Size allocated_size;
811 : :
812 : 1277 : newSpace = ShmemAllocRaw(size, 0, &allocated_size);
813 [ - + ]: 1277 : if (!newSpace)
814 [ # # ]: 0 : ereport(ERROR,
815 : : (errcode(ERRCODE_OUT_OF_MEMORY),
816 : : errmsg("out of shared memory (%zu bytes requested)",
817 : : size)));
818 : 1277 : return newSpace;
819 : : }
820 : :
821 : : /*
822 : : * ShmemAllocNoError -- allocate max-aligned chunk from shared memory
823 : : *
824 : : * As ShmemAlloc, but returns NULL if out of space, rather than erroring.
825 : : */
826 : : void *
827 : 0 : ShmemAllocNoError(Size size)
828 : : {
829 : : Size allocated_size;
830 : :
831 : 0 : return ShmemAllocRaw(size, 0, &allocated_size);
832 : : }
833 : :
834 : : /*
835 : : * ShmemAllocRaw -- allocate align chunk and return allocated size
836 : : *
837 : : * Also sets *allocated_size to the number of bytes allocated, which will
838 : : * be equal to the number requested plus any padding we choose to add.
839 : : */
840 : : static void *
841 : 100899 : ShmemAllocRaw(Size size, Size alignment, Size *allocated_size)
842 : : {
843 : : Size rawStart;
844 : : Size newStart;
845 : : Size newFree;
846 : : void *newSpace;
847 : :
848 : : /*
849 : : * Ensure all space is adequately aligned. We used to only MAXALIGN this
850 : : * space but experience has proved that on modern systems that is not good
851 : : * enough. Many parts of the system are very sensitive to critical data
852 : : * structures getting split across cache line boundaries. To avoid that,
853 : : * attempt to align the beginning of the allocation to a cache line
854 : : * boundary. The calling code will still need to be careful about how it
855 : : * uses the allocated space - e.g. by padding each element in an array of
856 : : * structures out to a power-of-two size - but without this, even that
857 : : * won't be sufficient.
858 : : */
859 [ + + ]: 100899 : if (alignment < PG_CACHE_LINE_SIZE)
860 : 97068 : alignment = PG_CACHE_LINE_SIZE;
861 : :
862 : : Assert(ShmemSegHdr != NULL);
863 : :
864 : 100899 : SpinLockAcquire(&ShmemAllocator->shmem_lock);
865 : :
866 : 100899 : rawStart = ShmemAllocator->free_offset;
867 : 100899 : newStart = TYPEALIGN(alignment, rawStart);
868 : :
869 : 100899 : newFree = newStart + size;
870 [ + + ]: 100899 : if (newFree <= ShmemSegHdr->totalsize)
871 : : {
872 : 100898 : newSpace = (char *) ShmemBase + newStart;
873 : 100898 : ShmemAllocator->free_offset = newFree;
874 : : }
875 : : else
876 : 1 : newSpace = NULL;
877 : :
878 : 100899 : SpinLockRelease(&ShmemAllocator->shmem_lock);
879 : :
880 : : /* note this assert is okay with newSpace == NULL */
881 : : Assert(newSpace == (void *) TYPEALIGN(alignment, newSpace));
882 : :
883 : 100899 : *allocated_size = newFree - rawStart;
884 : 100899 : return newSpace;
885 : : }
886 : :
887 : : /*
888 : : * ShmemAddrIsValid -- test if an address refers to shared memory
889 : : *
890 : : * Returns true if the pointer points within the shared memory segment.
891 : : */
892 : : bool
893 : 0 : ShmemAddrIsValid(const void *addr)
894 : : {
895 [ # # # # ]: 0 : return (addr >= ShmemBase) && (addr < ShmemEnd);
896 : : }
897 : :
898 : : /*
899 : : * Register callbacks that define a shared memory area (or multiple areas).
900 : : *
901 : : * The system will call the callbacks at different stages of postmaster or
902 : : * backend startup, to allocate and initialize the area.
903 : : *
904 : : * This is normally called early during postmaster startup, but if the
905 : : * SHMEM_CALLBACKS_ALLOW_AFTER_STARTUP is set, this can also be used after
906 : : * startup, although after startup there's no guarantee that there's enough
907 : : * shared memory available. When called after startup, this immediately calls
908 : : * the right callbacks depending on whether another backend had already
909 : : * initialized the area.
910 : : *
911 : : * Note: In EXEC_BACKEND mode, this needs to be called in every backend
912 : : * process. That's needed because we cannot pass down the callback function
913 : : * pointers from the postmaster process, because different processes may have
914 : : * loaded libraries to different addresses.
915 : : */
916 : : void
917 : 56704 : RegisterShmemCallbacks(const ShmemCallbacks *callbacks)
918 : : {
919 [ + + ]: 56704 : if (shmem_request_state == SRS_DONE)
920 : : {
921 : : /*
922 : : * After-startup initialization or attachment. Call the appropriate
923 : : * callbacks immediately.
924 : : *
925 : : * This is not allowed from the postmaster, because the postmaster
926 : : * cannot acquire locks.
927 : : */
928 [ - + ]: 8 : if ((callbacks->flags & SHMEM_CALLBACKS_ALLOW_AFTER_STARTUP) == 0)
929 [ # # ]: 0 : elog(ERROR, "cannot request shared memory at this time");
930 : : Assert(IsUnderPostmaster || !IsPostmasterEnvironment);
931 : :
932 : 8 : CallShmemCallbacksAfterStartup(callbacks);
933 : : }
934 [ + - ]: 56696 : else if (shmem_request_state == SRS_INITIAL)
935 : : {
936 : : /* Remember the callbacks for later */
937 : 56696 : registered_shmem_callbacks = lappend(registered_shmem_callbacks,
938 : : (void *) callbacks);
939 : : }
940 : : else
941 [ # # ]: 0 : elog(ERROR, "cannot request shared memory at this time");
942 : 56701 : }
943 : :
944 : : /*
945 : : * Register a shmem area (or multiple areas) after startup.
946 : : */
947 : : static void
948 : 8 : CallShmemCallbacksAfterStartup(const ShmemCallbacks *callbacks)
949 : : {
950 : : Assert(shmem_request_state == SRS_DONE);
951 : : Assert(pending_shmem_requests == NIL);
952 : :
953 [ + + ]: 8 : PG_TRY();
954 : : {
955 : 8 : shmem_request_state = SRS_REQUESTING;
956 : :
957 : : /*
958 : : * Call the request callback first. The callback makes
959 : : * ShmemRequest*() calls for each shmem area, adding them to
960 : : * pending_shmem_requests.
961 : : */
962 [ + - ]: 8 : if (callbacks->request_fn)
963 : 8 : callbacks->request_fn(callbacks->opaque_arg);
964 : :
965 : : /* Process all the requests */
966 : 8 : shmem_request_state = SRS_AFTER_STARTUP_ATTACH_OR_INIT;
967 [ + - ]: 8 : if (pending_shmem_requests != NIL)
968 : 8 : ProcessShmemRequestsAfterStartup(callbacks);
969 : : }
970 : 3 : PG_FINALLY();
971 : : {
972 [ + - + + : 24 : foreach_ptr(ShmemRequest, request, pending_shmem_requests)
+ + ]
973 : 8 : pfree(request->options);
974 : 8 : list_free_deep(pending_shmem_requests);
975 : 8 : pending_shmem_requests = NIL;
976 : :
977 : 8 : shmem_request_state = SRS_DONE;
978 : : }
979 [ + + ]: 8 : PG_END_TRY();
980 : 5 : }
981 : :
982 : : static void
983 : 8 : ProcessShmemRequestsAfterStartup(const ShmemCallbacks *callbacks)
984 : : {
985 : : bool found_any;
986 : : bool notfound_any;
987 : :
988 : : /* There should be some requests to process */
989 : : Assert(pending_shmem_requests != NIL);
990 : :
991 : : /* Caller manages the global state variable */
992 : : Assert(shmem_request_state == SRS_AFTER_STARTUP_ATTACH_OR_INIT);
993 : :
994 : : /*
995 : : * Hold ShmemIndexLock while we allocate all the shmem entries and run all
996 : : * the initializers.
997 : : */
998 : 8 : LWLockAcquire(ShmemIndexLock, LW_EXCLUSIVE);
999 : :
1000 : : /*
1001 : : * Check if the requested shared memory areas have already been
1002 : : * initialized. We assume all the areas requested by the request callback
1003 : : * to form a coherent unit such that they're all already initialized or
1004 : : * none. Otherwise it would be ambiguous which callback, init or attach,
1005 : : * to callback afterwards.
1006 : : */
1007 : 8 : found_any = notfound_any = false;
1008 [ + - + + : 22 : foreach_ptr(ShmemRequest, request, pending_shmem_requests)
+ + ]
1009 : : {
1010 : : ShmemIndexEnt *index_entry;
1011 : :
1012 : : index_entry = (ShmemIndexEnt *)
1013 : 8 : hash_search(ShmemIndex, request->options->name, HASH_FIND, NULL);
1014 [ + + ]: 8 : if (index_entry)
1015 : : {
1016 : : /*
1017 : : * Check for a half-initialized area. (See also similar check in
1018 : : * AttachShmemIndexEntry())
1019 : : */
1020 [ + + ]: 2 : if (!index_entry->initialized)
1021 [ + - ]: 1 : ereport(ERROR,
1022 : : (errmsg("cannot attach to shared memory struct \"%s\" because it was not fully initialized",
1023 : : request->options->name)));
1024 : 1 : found_any = true;
1025 : : }
1026 : : else
1027 : 6 : notfound_any = true;
1028 : : }
1029 [ + + - + ]: 7 : if (found_any && notfound_any)
1030 [ # # ]: 0 : elog(ERROR, "some of the requested shmem areas have already been initialized");
1031 : :
1032 : : /*
1033 : : * Allocate or attach all the shmem areas requested by the request_fn
1034 : : * callback.
1035 : : */
1036 [ + - + + : 19 : foreach_ptr(ShmemRequest, request, pending_shmem_requests)
+ + ]
1037 : : {
1038 [ + + ]: 7 : if (found_any)
1039 : 1 : AttachShmemIndexEntry(request, false);
1040 : : else
1041 : 6 : InitShmemIndexEntry(request);
1042 : : }
1043 : :
1044 : : /* Finish by calling the appropriate subsystem-specific callback */
1045 [ + + ]: 6 : if (found_any)
1046 : : {
1047 [ + - ]: 1 : if (callbacks->attach_fn)
1048 : 1 : callbacks->attach_fn(callbacks->opaque_arg);
1049 : : }
1050 : : else
1051 : : {
1052 [ + - ]: 5 : if (callbacks->init_fn)
1053 : 5 : callbacks->init_fn(callbacks->opaque_arg);
1054 : : }
1055 : :
1056 [ + - + + : 15 : foreach_ptr(ShmemRequest, request, pending_shmem_requests)
+ + ]
1057 : : {
1058 : 5 : request->index_entry->initialized = true;
1059 : : }
1060 : :
1061 : 5 : LWLockRelease(ShmemIndexLock);
1062 : 5 : }
1063 : :
1064 : : /*
1065 : : * Call all shmem request callbacks.
1066 : : */
1067 : : void
1068 : 1280 : ShmemCallRequestCallbacks(void)
1069 : : {
1070 : : ListCell *lc;
1071 : :
1072 : : Assert(shmem_request_state == SRS_INITIAL);
1073 : 1280 : shmem_request_state = SRS_REQUESTING;
1074 : :
1075 [ + - + + : 57626 : foreach(lc, registered_shmem_callbacks)
+ + ]
1076 : : {
1077 : 56346 : const ShmemCallbacks *callbacks = (const ShmemCallbacks *) lfirst(lc);
1078 : :
1079 [ + - ]: 56346 : if (callbacks->request_fn)
1080 : 56346 : callbacks->request_fn(callbacks->opaque_arg);
1081 : : }
1082 : 1280 : }
1083 : :
1084 : : /*
1085 : : * ShmemInitStruct -- Create/attach to a structure in shared memory.
1086 : : *
1087 : : * This is called during initialization to find or allocate
1088 : : * a data structure in shared memory. If no other process
1089 : : * has created the structure, this routine allocates space
1090 : : * for it. If it exists already, a pointer to the existing
1091 : : * structure is returned.
1092 : : *
1093 : : * Returns: pointer to the object. *foundPtr is set true if the object was
1094 : : * already in the shmem index (hence, already initialized).
1095 : : *
1096 : : * Note: This is a legacy interface, kept for backwards compatibility with
1097 : : * extensions. Use ShmemRequestStruct() in new code!
1098 : : */
1099 : : void *
1100 : 0 : ShmemInitStruct(const char *name, Size size, bool *foundPtr)
1101 : : {
1102 : 0 : void *ptr = NULL;
1103 : 0 : ShmemStructOpts options = {
1104 : : .name = name,
1105 : : .size = size,
1106 : : .ptr = &ptr,
1107 : : };
1108 : 0 : ShmemRequest request = {&options, SHMEM_KIND_STRUCT};
1109 : :
1110 : : Assert(shmem_request_state == SRS_DONE ||
1111 : : shmem_request_state == SRS_INITIALIZING ||
1112 : : shmem_request_state == SRS_REQUESTING);
1113 : :
1114 : 0 : LWLockAcquire(ShmemIndexLock, LW_EXCLUSIVE);
1115 : :
1116 : : /*
1117 : : * During postmaster startup, look up the existing entry if any.
1118 : : */
1119 : 0 : *foundPtr = false;
1120 [ # # ]: 0 : if (IsUnderPostmaster)
1121 : 0 : *foundPtr = AttachShmemIndexEntry(&request, true);
1122 : :
1123 : : /* Initialize it if not found */
1124 [ # # ]: 0 : if (!*foundPtr)
1125 : : {
1126 : 0 : InitShmemIndexEntry(&request);
1127 : : /* no additional initialization needed */
1128 : 0 : request.index_entry->initialized = true;
1129 : : }
1130 : :
1131 : 0 : LWLockRelease(ShmemIndexLock);
1132 : :
1133 : : Assert(ptr != NULL);
1134 : 0 : return ptr;
1135 : : }
1136 : :
1137 : : /* SQL SRF showing allocated shared memory */
1138 : : Datum
1139 : 4 : pg_get_shmem_allocations(PG_FUNCTION_ARGS)
1140 : : {
1141 : : #define PG_GET_SHMEM_SIZES_COLS 4
1142 : 4 : ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
1143 : : HASH_SEQ_STATUS hstat;
1144 : : ShmemIndexEnt *ent;
1145 : 4 : Size named_allocated = 0;
1146 : : Datum values[PG_GET_SHMEM_SIZES_COLS];
1147 : : bool nulls[PG_GET_SHMEM_SIZES_COLS];
1148 : :
1149 : 4 : InitMaterializedSRF(fcinfo, 0);
1150 : :
1151 : 4 : LWLockAcquire(ShmemIndexLock, LW_SHARED);
1152 : :
1153 : 4 : hash_seq_init(&hstat, ShmemIndex);
1154 : :
1155 : : /* output all allocated entries */
1156 : 4 : memset(nulls, 0, sizeof(nulls));
1157 [ + + ]: 322 : while ((ent = (ShmemIndexEnt *) hash_seq_search(&hstat)) != NULL)
1158 : : {
1159 : 318 : values[0] = CStringGetTextDatum(ent->key);
1160 : 318 : values[1] = Int64GetDatum((char *) ent->location - (char *) ShmemSegHdr);
1161 : 318 : values[2] = Int64GetDatum(ent->size);
1162 : 318 : values[3] = Int64GetDatum(ent->allocated_size);
1163 : 318 : named_allocated += ent->allocated_size;
1164 : :
1165 : 318 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
1166 : : values, nulls);
1167 : : }
1168 : :
1169 : : /* output shared memory allocated but not counted via the shmem index */
1170 : 4 : values[0] = CStringGetTextDatum("<anonymous>");
1171 : 4 : nulls[1] = true;
1172 : 4 : values[2] = Int64GetDatum(ShmemAllocator->free_offset - named_allocated);
1173 : 4 : values[3] = values[2];
1174 : 4 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
1175 : :
1176 : : /* output as-of-yet unused shared memory */
1177 : 4 : nulls[0] = true;
1178 : 4 : values[1] = Int64GetDatum(ShmemAllocator->free_offset);
1179 : 4 : nulls[1] = false;
1180 : 4 : values[2] = Int64GetDatum(ShmemSegHdr->totalsize - ShmemAllocator->free_offset);
1181 : 4 : values[3] = values[2];
1182 : 4 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
1183 : :
1184 : 4 : LWLockRelease(ShmemIndexLock);
1185 : :
1186 : 4 : return (Datum) 0;
1187 : : }
1188 : :
1189 : : /*
1190 : : * SQL SRF showing NUMA memory nodes for allocated shared memory
1191 : : *
1192 : : * Compared to pg_get_shmem_allocations(), this function does not return
1193 : : * information about shared anonymous allocations and unused shared memory.
1194 : : */
1195 : : Datum
1196 : 4 : pg_get_shmem_allocations_numa(PG_FUNCTION_ARGS)
1197 : : {
1198 : : #define PG_GET_SHMEM_NUMA_SIZES_COLS 3
1199 : 4 : ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
1200 : : HASH_SEQ_STATUS hstat;
1201 : : ShmemIndexEnt *ent;
1202 : : Datum values[PG_GET_SHMEM_NUMA_SIZES_COLS];
1203 : : bool nulls[PG_GET_SHMEM_NUMA_SIZES_COLS];
1204 : : Size os_page_size;
1205 : : void **page_ptrs;
1206 : : int *pages_status;
1207 : : uint64 shm_total_page_count,
1208 : : shm_ent_page_count,
1209 : : max_nodes;
1210 : : Size *nodes;
1211 : :
1212 [ + - ]: 4 : if (pg_numa_init() == -1)
1213 [ + - ]: 4 : elog(ERROR, "libnuma initialization failed or NUMA is not supported on this platform");
1214 : :
1215 : 0 : InitMaterializedSRF(fcinfo, 0);
1216 : :
1217 : 0 : max_nodes = pg_numa_get_max_node();
1218 : 0 : nodes = palloc_array(Size, max_nodes + 2);
1219 : :
1220 : : /*
1221 : : * Shared memory allocations can vary in size and may not align with OS
1222 : : * memory page boundaries, while NUMA queries work on pages.
1223 : : *
1224 : : * To correctly map each allocation to NUMA nodes, we need to: 1.
1225 : : * Determine the OS memory page size. 2. Align each allocation's start/end
1226 : : * addresses to page boundaries. 3. Query NUMA node information for all
1227 : : * pages spanning the allocation.
1228 : : */
1229 : 0 : os_page_size = pg_get_shmem_pagesize();
1230 : :
1231 : : /*
1232 : : * Allocate memory for page pointers and status based on total shared
1233 : : * memory size. This simplified approach allocates enough space for all
1234 : : * pages in shared memory rather than calculating the exact requirements
1235 : : * for each segment.
1236 : : *
1237 : : * Add 1, because we don't know how exactly the segments align to OS
1238 : : * pages, so the allocation might use one more memory page. In practice
1239 : : * this is not very likely, and moreover we have more entries, each of
1240 : : * them using only fraction of the total pages.
1241 : : */
1242 : 0 : shm_total_page_count = (ShmemSegHdr->totalsize / os_page_size) + 1;
1243 : 0 : page_ptrs = palloc0_array(void *, shm_total_page_count);
1244 : 0 : pages_status = palloc_array(int, shm_total_page_count);
1245 : :
1246 [ # # ]: 0 : if (firstNumaTouch)
1247 [ # # ]: 0 : elog(DEBUG1, "NUMA: page-faulting shared memory segments for proper NUMA readouts");
1248 : :
1249 : 0 : LWLockAcquire(ShmemIndexLock, LW_SHARED);
1250 : :
1251 : 0 : hash_seq_init(&hstat, ShmemIndex);
1252 : :
1253 : : /* output all allocated entries */
1254 [ # # ]: 0 : while ((ent = (ShmemIndexEnt *) hash_seq_search(&hstat)) != NULL)
1255 : : {
1256 : : char *startptr,
1257 : : *endptr;
1258 : : Size total_len;
1259 : :
1260 : : /*
1261 : : * Calculate the range of OS pages used by this segment. The segment
1262 : : * may start / end half-way through a page, we want to count these
1263 : : * pages too. So we align the start/end pointers down/up, and then
1264 : : * calculate the number of pages from that.
1265 : : */
1266 : 0 : startptr = (char *) TYPEALIGN_DOWN(os_page_size, ent->location);
1267 : 0 : endptr = (char *) TYPEALIGN(os_page_size,
1268 : : (char *) ent->location + ent->allocated_size);
1269 : 0 : total_len = (endptr - startptr);
1270 : :
1271 : 0 : shm_ent_page_count = total_len / os_page_size;
1272 : :
1273 : : /*
1274 : : * If we ever get 0xff (-1) back from kernel inquiry, then we probably
1275 : : * have a bug in mapping buffers to OS pages.
1276 : : */
1277 : 0 : memset(pages_status, 0xff, sizeof(int) * shm_ent_page_count);
1278 : :
1279 : : /*
1280 : : * Setup page_ptrs[] with pointers to all OS pages for this segment,
1281 : : * and get the NUMA status using pg_numa_query_pages.
1282 : : *
1283 : : * In order to get reliable results we also need to touch memory
1284 : : * pages, so that inquiry about NUMA memory node doesn't return -2
1285 : : * (ENOENT, which indicates unmapped/unallocated pages).
1286 : : */
1287 [ # # ]: 0 : for (uint64 i = 0; i < shm_ent_page_count; i++)
1288 : : {
1289 : 0 : page_ptrs[i] = startptr + (i * os_page_size);
1290 : :
1291 : 0 : if (firstNumaTouch)
1292 : : pg_numa_touch_mem_if_required(page_ptrs[i]);
1293 : :
1294 [ # # ]: 0 : CHECK_FOR_INTERRUPTS();
1295 : : }
1296 : :
1297 [ # # ]: 0 : if (pg_numa_query_pages(0, shm_ent_page_count, page_ptrs, pages_status) == -1)
1298 [ # # ]: 0 : elog(ERROR, "failed NUMA pages inquiry status: %m");
1299 : :
1300 : : /* Count number of NUMA nodes used for this shared memory entry */
1301 : 0 : memset(nodes, 0, sizeof(Size) * (max_nodes + 2));
1302 : :
1303 [ # # ]: 0 : for (uint64 i = 0; i < shm_ent_page_count; i++)
1304 : : {
1305 : 0 : int s = pages_status[i];
1306 : :
1307 : : /* Ensure we are adding only valid index to the array */
1308 [ # # # # ]: 0 : if (s >= 0 && s <= max_nodes)
1309 : : {
1310 : : /* valid NUMA node */
1311 : 0 : nodes[s]++;
1312 : 0 : continue;
1313 : : }
1314 [ # # ]: 0 : else if (s == -2)
1315 : : {
1316 : : /* -2 means ENOENT (e.g. page was moved to swap) */
1317 : 0 : nodes[max_nodes + 1]++;
1318 : 0 : continue;
1319 : : }
1320 : :
1321 [ # # ]: 0 : elog(ERROR, "invalid NUMA node id outside of allowed range "
1322 : : "[0, " UINT64_FORMAT "]: %d", max_nodes, s);
1323 : : }
1324 : :
1325 : : /* no NULLs for regular nodes */
1326 : 0 : memset(nulls, 0, sizeof(nulls));
1327 : :
1328 : : /*
1329 : : * Add one entry for each NUMA node, including those without allocated
1330 : : * memory for this segment.
1331 : : */
1332 [ # # ]: 0 : for (uint64 i = 0; i <= max_nodes; i++)
1333 : : {
1334 : 0 : values[0] = CStringGetTextDatum(ent->key);
1335 : 0 : values[1] = Int32GetDatum(i);
1336 : 0 : values[2] = Int64GetDatum(nodes[i] * os_page_size);
1337 : :
1338 : 0 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
1339 : : values, nulls);
1340 : : }
1341 : :
1342 : : /* The last entry is used for pages without a NUMA node. */
1343 : 0 : nulls[1] = true;
1344 : 0 : values[0] = CStringGetTextDatum(ent->key);
1345 : 0 : values[2] = Int64GetDatum(nodes[max_nodes + 1] * os_page_size);
1346 : :
1347 : 0 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
1348 : : values, nulls);
1349 : : }
1350 : :
1351 : 0 : LWLockRelease(ShmemIndexLock);
1352 : 0 : firstNumaTouch = false;
1353 : :
1354 : 0 : return (Datum) 0;
1355 : : }
1356 : :
1357 : : /*
1358 : : * Determine the memory page size used for the shared memory segment.
1359 : : *
1360 : : * If the shared segment was allocated using huge pages, returns the size of
1361 : : * a huge page. Otherwise returns the size of regular memory page.
1362 : : *
1363 : : * This should be used only after the server is started.
1364 : : */
1365 : : Size
1366 : 2 : pg_get_shmem_pagesize(void)
1367 : : {
1368 : : Size os_page_size;
1369 : : #ifdef WIN32
1370 : : SYSTEM_INFO sysinfo;
1371 : :
1372 : : GetSystemInfo(&sysinfo);
1373 : : os_page_size = sysinfo.dwPageSize;
1374 : : #else
1375 : 2 : os_page_size = sysconf(_SC_PAGESIZE);
1376 : : #endif
1377 : :
1378 : : Assert(IsUnderPostmaster);
1379 : : Assert(huge_pages_status != HUGE_PAGES_UNKNOWN);
1380 : :
1381 [ - + ]: 2 : if (huge_pages_status == HUGE_PAGES_ON)
1382 : 0 : GetHugePageSize(&os_page_size, NULL);
1383 : :
1384 : 2 : return os_page_size;
1385 : : }
1386 : :
1387 : : Datum
1388 : 5 : pg_numa_available(PG_FUNCTION_ARGS)
1389 : : {
1390 : 5 : PG_RETURN_BOOL(pg_numa_init() != -1);
1391 : : }
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