Branch data Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * slab.c
4 : : * SLAB allocator definitions.
5 : : *
6 : : * SLAB is a MemoryContext implementation designed for cases where large
7 : : * numbers of equally-sized objects can be allocated and freed efficiently
8 : : * with minimal memory wastage and fragmentation.
9 : : *
10 : : *
11 : : * Portions Copyright (c) 2017-2026, PostgreSQL Global Development Group
12 : : *
13 : : * IDENTIFICATION
14 : : * src/backend/utils/mmgr/slab.c
15 : : *
16 : : *
17 : : * NOTE:
18 : : * The constant allocation size allows significant simplification and various
19 : : * optimizations over more general purpose allocators. The blocks are carved
20 : : * into chunks of exactly the right size, wasting only the space required to
21 : : * MAXALIGN the allocated chunks.
22 : : *
23 : : * Slab can also help reduce memory fragmentation in cases where longer-lived
24 : : * chunks remain stored on blocks while most of the other chunks have already
25 : : * been pfree'd. We give priority to putting new allocations into the
26 : : * "fullest" block. This help avoid having too many sparsely used blocks
27 : : * around and allows blocks to more easily become completely unused which
28 : : * allows them to be eventually free'd.
29 : : *
30 : : * We identify the "fullest" block to put new allocations on by using a block
31 : : * from the lowest populated element of the context's "blocklist" array.
32 : : * This is an array of dlists containing blocks which we partition by the
33 : : * number of free chunks which block has. Blocks with fewer free chunks are
34 : : * stored in a lower indexed dlist array slot. Full blocks go on the 0th
35 : : * element of the blocklist array. So that we don't have to have too many
36 : : * elements in the array, each dlist in the array is responsible for a range
37 : : * of free chunks. When a chunk is palloc'd or pfree'd we may need to move
38 : : * the block onto another dlist if the number of free chunks crosses the
39 : : * range boundary that the current list is responsible for. Having just a
40 : : * few blocklist elements reduces the number of times we must move the block
41 : : * onto another dlist element.
42 : : *
43 : : * We keep track of free chunks within each block by using a block-level free
44 : : * list. We consult this list when we allocate a new chunk in the block.
45 : : * The free list is a linked list, the head of which is pointed to with
46 : : * SlabBlock's freehead field. Each subsequent list item is stored in the
47 : : * free chunk's memory. We ensure chunks are large enough to store this
48 : : * address.
49 : : *
50 : : * When we allocate a new block, technically all chunks are free, however, to
51 : : * avoid having to write out the entire block to set the linked list for the
52 : : * free chunks for every chunk in the block, we instead store a pointer to
53 : : * the next "unused" chunk on the block and keep track of how many of these
54 : : * unused chunks there are. When a new block is malloc'd, all chunks are
55 : : * unused. The unused pointer starts with the first chunk on the block and
56 : : * as chunks are allocated, the unused pointer is incremented. As chunks are
57 : : * pfree'd, the unused pointer never goes backwards. The unused pointer can
58 : : * be thought of as a high watermark for the maximum number of chunks in the
59 : : * block which have been in use concurrently. When a chunk is pfree'd the
60 : : * chunk is put onto the head of the free list and the unused pointer is not
61 : : * changed. We only consume more unused chunks if we run out of free chunks
62 : : * on the free list. This method effectively gives priority to using
63 : : * previously used chunks over previously unused chunks, which should perform
64 : : * better due to CPU caching effects.
65 : : *
66 : : *-------------------------------------------------------------------------
67 : : */
68 : :
69 : : #include "postgres.h"
70 : :
71 : : #include "lib/ilist.h"
72 : : #include "utils/memdebug.h"
73 : : #include "utils/memutils.h"
74 : : #include "utils/memutils_internal.h"
75 : : #include "utils/memutils_memorychunk.h"
76 : :
77 : : #define Slab_BLOCKHDRSZ MAXALIGN(sizeof(SlabBlock))
78 : :
79 : : #ifdef MEMORY_CONTEXT_CHECKING
80 : : /*
81 : : * Size of the memory required to store the SlabContext.
82 : : * MEMORY_CONTEXT_CHECKING builds need some extra memory for the isChunkFree
83 : : * array.
84 : : */
85 : : #define Slab_CONTEXT_HDRSZ(chunksPerBlock) \
86 : : (sizeof(SlabContext) + ((chunksPerBlock) * sizeof(bool)))
87 : : #else
88 : : #define Slab_CONTEXT_HDRSZ(chunksPerBlock) sizeof(SlabContext)
89 : : #endif
90 : :
91 : : /*
92 : : * The number of partitions to divide the blocklist into based their number of
93 : : * free chunks. There must be at least 2.
94 : : */
95 : : #define SLAB_BLOCKLIST_COUNT 3
96 : :
97 : : /* The maximum number of completely empty blocks to keep around for reuse. */
98 : : #define SLAB_MAXIMUM_EMPTY_BLOCKS 10
99 : :
100 : : /*
101 : : * SlabContext is a specialized implementation of MemoryContext.
102 : : */
103 : : typedef struct SlabContext
104 : : {
105 : : MemoryContextData header; /* Standard memory-context fields */
106 : : /* Allocation parameters for this context: */
107 : : uint32 chunkSize; /* the requested (non-aligned) chunk size */
108 : : uint32 fullChunkSize; /* chunk size with chunk header and alignment */
109 : : uint32 blockSize; /* the size to make each block of chunks */
110 : : int32 chunksPerBlock; /* number of chunks that fit in 1 block */
111 : : int32 curBlocklistIndex; /* index into the blocklist[] element
112 : : * containing the fullest, blocks */
113 : : #ifdef MEMORY_CONTEXT_CHECKING
114 : : bool *isChunkFree; /* array to mark free chunks in a block during
115 : : * SlabCheck */
116 : : #endif
117 : :
118 : : int32 blocklist_shift; /* number of bits to shift the nfree count
119 : : * by to get the index into blocklist[] */
120 : : dclist_head emptyblocks; /* empty blocks to use up first instead of
121 : : * mallocing new blocks */
122 : :
123 : : /*
124 : : * Blocks with free space, grouped by the number of free chunks they
125 : : * contain. Completely full blocks are stored in the 0th element.
126 : : * Completely empty blocks are stored in emptyblocks or free'd if we have
127 : : * enough empty blocks already.
128 : : */
129 : : dlist_head blocklist[SLAB_BLOCKLIST_COUNT];
130 : : } SlabContext;
131 : :
132 : : /*
133 : : * SlabBlock
134 : : * Structure of a single slab block.
135 : : *
136 : : * slab: pointer back to the owning MemoryContext
137 : : * nfree: number of chunks on the block which are unallocated
138 : : * nunused: number of chunks on the block unallocated and not on the block's
139 : : * freelist.
140 : : * freehead: linked-list header storing a pointer to the first free chunk on
141 : : * the block. Subsequent pointers are stored in the chunk's memory. NULL
142 : : * indicates the end of the list.
143 : : * unused: pointer to the next chunk which has yet to be used.
144 : : * node: doubly-linked list node for the context's blocklist
145 : : */
146 : : typedef struct SlabBlock
147 : : {
148 : : SlabContext *slab; /* owning context */
149 : : int32 nfree; /* number of chunks on free + unused chunks */
150 : : int32 nunused; /* number of unused chunks */
151 : : MemoryChunk *freehead; /* pointer to the first free chunk */
152 : : MemoryChunk *unused; /* pointer to the next unused chunk */
153 : : dlist_node node; /* doubly-linked list for blocklist[] */
154 : : } SlabBlock;
155 : :
156 : :
157 : : #define Slab_CHUNKHDRSZ sizeof(MemoryChunk)
158 : : #define SlabChunkGetPointer(chk) \
159 : : ((void *) (((char *) (chk)) + sizeof(MemoryChunk)))
160 : :
161 : : /*
162 : : * SlabBlockGetChunk
163 : : * Obtain a pointer to the nth (0-based) chunk in the block
164 : : */
165 : : #define SlabBlockGetChunk(slab, block, n) \
166 : : ((MemoryChunk *) ((char *) (block) + Slab_BLOCKHDRSZ \
167 : : + ((n) * (slab)->fullChunkSize)))
168 : :
169 : : #if defined(MEMORY_CONTEXT_CHECKING) || defined(USE_ASSERT_CHECKING)
170 : :
171 : : /*
172 : : * SlabChunkIndex
173 : : * Get the 0-based index of how many chunks into the block the given
174 : : * chunk is.
175 : : */
176 : : #define SlabChunkIndex(slab, block, chunk) \
177 : : (((char *) (chunk) - (char *) SlabBlockGetChunk(slab, block, 0)) / \
178 : : (slab)->fullChunkSize)
179 : :
180 : : /*
181 : : * SlabChunkMod
182 : : * A MemoryChunk should always be at an address which is a multiple of
183 : : * fullChunkSize starting from the 0th chunk position. This will return
184 : : * non-zero if it's not.
185 : : */
186 : : #define SlabChunkMod(slab, block, chunk) \
187 : : (((char *) (chunk) - (char *) SlabBlockGetChunk(slab, block, 0)) % \
188 : : (slab)->fullChunkSize)
189 : :
190 : : #endif
191 : :
192 : : /*
193 : : * SlabIsValid
194 : : * True iff set is a valid slab allocation set.
195 : : */
196 : : #define SlabIsValid(set) ((set) && IsA(set, SlabContext))
197 : :
198 : : /*
199 : : * SlabBlockIsValid
200 : : * True iff block is a valid block of slab allocation set.
201 : : */
202 : : #define SlabBlockIsValid(block) \
203 : : ((block) && SlabIsValid((block)->slab))
204 : :
205 : : /*
206 : : * SlabBlocklistIndex
207 : : * Determine the blocklist index that a block should be in for the given
208 : : * number of free chunks.
209 : : */
210 : : static inline int32
211 : 2266 : SlabBlocklistIndex(SlabContext *slab, int nfree)
212 : : {
213 : 2266 : int32 index;
214 : 2266 : int32 blocklist_shift = slab->blocklist_shift;
215 : :
216 [ + - ]: 2266 : Assert(nfree >= 0 && nfree <= slab->chunksPerBlock);
217 : :
218 : : /*
219 : : * Determine the blocklist index based on the number of free chunks. We
220 : : * must ensure that 0 free chunks is dedicated to index 0. Everything
221 : : * else must be >= 1 and < SLAB_BLOCKLIST_COUNT.
222 : : *
223 : : * To make this as efficient as possible, we exploit some two's complement
224 : : * arithmetic where we reverse the sign before bit shifting. This results
225 : : * in an nfree of 0 using index 0 and anything non-zero staying non-zero.
226 : : * This is exploiting 0 and -0 being the same in two's complement. When
227 : : * we're done, we just need to flip the sign back over again for a
228 : : * positive index.
229 : : */
230 : 2266 : index = -((-nfree) >> blocklist_shift);
231 : :
232 [ + - ]: 2266 : if (nfree == 0)
233 [ # # ]: 0 : Assert(index == 0);
234 : : else
235 [ + - ]: 2266 : Assert(index >= 1 && index < SLAB_BLOCKLIST_COUNT);
236 : :
237 : 4532 : return index;
238 : 2266 : }
239 : :
240 : : /*
241 : : * SlabFindNextBlockListIndex
242 : : * Search blocklist for blocks which have free chunks and return the
243 : : * index of the blocklist found containing at least 1 block with free
244 : : * chunks. If no block can be found we return 0.
245 : : *
246 : : * Note: We give priority to fuller blocks so that these are filled before
247 : : * emptier blocks. This is done to increase the chances that mostly-empty
248 : : * blocks will eventually become completely empty so they can be free'd.
249 : : */
250 : : static int32
251 : 41 : SlabFindNextBlockListIndex(SlabContext *slab)
252 : : {
253 : : /* start at 1 as blocklist[0] is for full blocks. */
254 [ + + - - : 123 : for (int i = 1; i < SLAB_BLOCKLIST_COUNT; i++)
+ ]
255 : : {
256 : : /* return the first found non-empty index */
257 [ - + ]: 82 : if (!dlist_is_empty(&slab->blocklist[i]))
258 : 0 : return i;
259 : 82 : }
260 : :
261 : : /* no blocks with free space */
262 : 41 : return 0;
263 : 41 : }
264 : :
265 : : /*
266 : : * SlabGetNextFreeChunk
267 : : * Return the next free chunk in block and update the block to account
268 : : * for the returned chunk now being used.
269 : : */
270 : : static inline MemoryChunk *
271 : 5 : SlabGetNextFreeChunk(SlabContext *slab, SlabBlock *block)
272 : : {
273 : 5 : MemoryChunk *chunk;
274 : :
275 [ + - ]: 5 : Assert(block->nfree > 0);
276 : :
277 [ + + ]: 5 : if (block->freehead != NULL)
278 : : {
279 : 4 : chunk = block->freehead;
280 : :
281 : : /*
282 : : * Pop the chunk from the linked list of free chunks. The pointer to
283 : : * the next free chunk is stored in the chunk itself.
284 : : */
285 : 4 : VALGRIND_MAKE_MEM_DEFINED(SlabChunkGetPointer(chunk), sizeof(MemoryChunk *));
286 : 4 : block->freehead = *(MemoryChunk **) SlabChunkGetPointer(chunk);
287 : :
288 : : /* check nothing stomped on the free chunk's memory */
289 [ + - # # ]: 4 : Assert(block->freehead == NULL ||
290 : : (block->freehead >= SlabBlockGetChunk(slab, block, 0) &&
291 : : block->freehead <= SlabBlockGetChunk(slab, block, slab->chunksPerBlock - 1) &&
292 : : SlabChunkMod(slab, block, block->freehead) == 0));
293 : 4 : }
294 : : else
295 : : {
296 [ + - ]: 1 : Assert(block->nunused > 0);
297 : :
298 : 1 : chunk = block->unused;
299 : 1 : block->unused = (MemoryChunk *) (((char *) block->unused) + slab->fullChunkSize);
300 : 1 : block->nunused--;
301 : : }
302 : :
303 : 5 : block->nfree--;
304 : :
305 : 10 : return chunk;
306 : 5 : }
307 : :
308 : : /*
309 : : * SlabContextCreate
310 : : * Create a new Slab context.
311 : : *
312 : : * parent: parent context, or NULL if top-level context
313 : : * name: name of context (must be statically allocated)
314 : : * blockSize: allocation block size
315 : : * chunkSize: allocation chunk size
316 : : *
317 : : * The Slab_CHUNKHDRSZ + MAXALIGN(chunkSize + 1) may not exceed
318 : : * MEMORYCHUNK_MAX_VALUE.
319 : : * 'blockSize' may not exceed MEMORYCHUNK_MAX_BLOCKOFFSET.
320 : : */
321 : : MemoryContext
322 : 3485 : SlabContextCreate(MemoryContext parent,
323 : : const char *name,
324 : : Size blockSize,
325 : : Size chunkSize)
326 : : {
327 : 3485 : int chunksPerBlock;
328 : 3485 : Size fullChunkSize;
329 : 3485 : SlabContext *slab;
330 : 3485 : int i;
331 : :
332 : : /* ensure MemoryChunk's size is properly maxaligned */
333 : : StaticAssertDecl(Slab_CHUNKHDRSZ == MAXALIGN(Slab_CHUNKHDRSZ),
334 : : "sizeof(MemoryChunk) is not maxaligned");
335 [ + - ]: 3485 : Assert(blockSize <= MEMORYCHUNK_MAX_BLOCKOFFSET);
336 : :
337 : : /*
338 : : * Ensure there's enough space to store the pointer to the next free chunk
339 : : * in the memory of the (otherwise) unused allocation.
340 : : */
341 [ + - ]: 3485 : if (chunkSize < sizeof(MemoryChunk *))
342 : 0 : chunkSize = sizeof(MemoryChunk *);
343 : :
344 : : /* length of the maxaligned chunk including the chunk header */
345 : : #ifdef MEMORY_CONTEXT_CHECKING
346 : : /* ensure there's always space for the sentinel byte */
347 : 3485 : fullChunkSize = Slab_CHUNKHDRSZ + MAXALIGN(chunkSize + 1);
348 : : #else
349 : : fullChunkSize = Slab_CHUNKHDRSZ + MAXALIGN(chunkSize);
350 : : #endif
351 : :
352 [ + - ]: 3485 : Assert(fullChunkSize <= MEMORYCHUNK_MAX_VALUE);
353 : :
354 : : /* compute the number of chunks that will fit on each block */
355 : 3485 : chunksPerBlock = (blockSize - Slab_BLOCKHDRSZ) / fullChunkSize;
356 : :
357 : : /* Make sure the block can store at least one chunk. */
358 [ + - ]: 3485 : if (chunksPerBlock == 0)
359 [ # # # # ]: 0 : elog(ERROR, "block size %zu for slab is too small for %zu-byte chunks",
360 : : blockSize, chunkSize);
361 : :
362 : :
363 : :
364 : 3485 : slab = (SlabContext *) malloc(Slab_CONTEXT_HDRSZ(chunksPerBlock));
365 [ + - ]: 3485 : if (slab == NULL)
366 : : {
367 : 0 : MemoryContextStats(TopMemoryContext);
368 [ # # # # ]: 0 : ereport(ERROR,
369 : : (errcode(ERRCODE_OUT_OF_MEMORY),
370 : : errmsg("out of memory"),
371 : : errdetail("Failed while creating memory context \"%s\".",
372 : : name)));
373 : 0 : }
374 : :
375 : : /*
376 : : * Avoid writing code that can fail between here and MemoryContextCreate;
377 : : * we'd leak the header if we ereport in this stretch.
378 : : */
379 : :
380 : : /* See comments about Valgrind interactions in aset.c */
381 : 3485 : VALGRIND_CREATE_MEMPOOL(slab, 0, false);
382 : : /* This vchunk covers the SlabContext only */
383 : 3485 : VALGRIND_MEMPOOL_ALLOC(slab, slab, sizeof(SlabContext));
384 : :
385 : : /* Fill in SlabContext-specific header fields */
386 : 3485 : slab->chunkSize = (uint32) chunkSize;
387 : 3485 : slab->fullChunkSize = (uint32) fullChunkSize;
388 : 3485 : slab->blockSize = (uint32) blockSize;
389 : 3485 : slab->chunksPerBlock = chunksPerBlock;
390 : 3485 : slab->curBlocklistIndex = 0;
391 : :
392 : : /*
393 : : * Compute a shift that guarantees that shifting chunksPerBlock with it is
394 : : * < SLAB_BLOCKLIST_COUNT - 1. The reason that we subtract 1 from
395 : : * SLAB_BLOCKLIST_COUNT in this calculation is that we reserve the 0th
396 : : * blocklist element for blocks which have no free chunks.
397 : : *
398 : : * We calculate the number of bits to shift by rather than a divisor to
399 : : * divide by as performing division each time we need to find the
400 : : * blocklist index would be much slower.
401 : : */
402 : 3485 : slab->blocklist_shift = 0;
403 [ + + ]: 21607 : while ((slab->chunksPerBlock >> slab->blocklist_shift) >= (SLAB_BLOCKLIST_COUNT - 1))
404 : 18122 : slab->blocklist_shift++;
405 : :
406 : : /* initialize the list to store empty blocks to be reused */
407 : 3485 : dclist_init(&slab->emptyblocks);
408 : :
409 : : /* initialize each blocklist slot */
410 [ + + ]: 13940 : for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
411 : 10455 : dlist_init(&slab->blocklist[i]);
412 : :
413 : : #ifdef MEMORY_CONTEXT_CHECKING
414 : : /* set the isChunkFree pointer right after the end of the context */
415 : 3485 : slab->isChunkFree = (bool *) ((char *) slab + sizeof(SlabContext));
416 : : #endif
417 : :
418 : : /* Finally, do the type-independent part of context creation */
419 : 6970 : MemoryContextCreate((MemoryContext) slab,
420 : : T_SlabContext,
421 : : MCTX_SLAB_ID,
422 : 3485 : parent,
423 : 3485 : name);
424 : :
425 : 6970 : return (MemoryContext) slab;
426 : 3485 : }
427 : :
428 : : /*
429 : : * SlabReset
430 : : * Frees all memory which is allocated in the given set.
431 : : *
432 : : * The code simply frees all the blocks in the context - we don't keep any
433 : : * keeper blocks or anything like that.
434 : : */
435 : : void
436 : 3485 : SlabReset(MemoryContext context)
437 : : {
438 : 3485 : SlabContext *slab = (SlabContext *) context;
439 : 3485 : dlist_mutable_iter miter;
440 : 3485 : int i;
441 : :
442 [ + - ]: 3485 : Assert(SlabIsValid(slab));
443 : :
444 : : #ifdef MEMORY_CONTEXT_CHECKING
445 : : /* Check for corruption and leaks before freeing */
446 : 3485 : SlabCheck(context);
447 : : #endif
448 : :
449 : : /* release any retained empty blocks */
450 [ + - + + ]: 3522 : dclist_foreach_modify(miter, &slab->emptyblocks)
451 : : {
452 : 37 : SlabBlock *block = dlist_container(SlabBlock, node, miter.cur);
453 : :
454 : 37 : dclist_delete_from(&slab->emptyblocks, miter.cur);
455 : :
456 : : #ifdef CLOBBER_FREED_MEMORY
457 : 37 : wipe_mem(block, slab->blockSize);
458 : : #endif
459 : :
460 : : /* As in aset.c, free block-header vchunks explicitly */
461 : 37 : VALGRIND_MEMPOOL_FREE(slab, block);
462 : :
463 : 37 : free(block);
464 : 37 : context->mem_allocated -= slab->blockSize;
465 : 37 : }
466 : :
467 : : /* walk over blocklist and free the blocks */
468 [ + + ]: 13940 : for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
469 : : {
470 [ + - + + ]: 11154 : dlist_foreach_modify(miter, &slab->blocklist[i])
471 : : {
472 : 699 : SlabBlock *block = dlist_container(SlabBlock, node, miter.cur);
473 : :
474 : 699 : dlist_delete(miter.cur);
475 : :
476 : : #ifdef CLOBBER_FREED_MEMORY
477 : 699 : wipe_mem(block, slab->blockSize);
478 : : #endif
479 : :
480 : : /* As in aset.c, free block-header vchunks explicitly */
481 : 699 : VALGRIND_MEMPOOL_FREE(slab, block);
482 : :
483 : 699 : free(block);
484 : 699 : context->mem_allocated -= slab->blockSize;
485 : 699 : }
486 : 10455 : }
487 : :
488 : : /*
489 : : * Instruct Valgrind to throw away all the vchunks associated with this
490 : : * context, except for the one covering the SlabContext. This gets rid of
491 : : * the vchunks for whatever user data is getting discarded by the context
492 : : * reset.
493 : : */
494 : 3485 : VALGRIND_MEMPOOL_TRIM(slab, slab, sizeof(SlabContext));
495 : :
496 : 3485 : slab->curBlocklistIndex = 0;
497 : :
498 [ + - ]: 3485 : Assert(context->mem_allocated == 0);
499 : 3485 : }
500 : :
501 : : /*
502 : : * SlabDelete
503 : : * Free all memory which is allocated in the given context.
504 : : */
505 : : void
506 : 3485 : SlabDelete(MemoryContext context)
507 : : {
508 : : /* Reset to release all the SlabBlocks */
509 : 3485 : SlabReset(context);
510 : :
511 : : /* Destroy the vpool -- see notes in aset.c */
512 : 3485 : VALGRIND_DESTROY_MEMPOOL(context);
513 : :
514 : : /* And free the context header */
515 : 3485 : free(context);
516 : 3485 : }
517 : :
518 : : /*
519 : : * Small helper for allocating a new chunk from a chunk, to avoid duplicating
520 : : * the code between SlabAlloc() and SlabAllocFromNewBlock().
521 : : */
522 : : static inline void *
523 : 741 : SlabAllocSetupNewChunk(MemoryContext context, SlabBlock *block,
524 : : MemoryChunk *chunk, Size size)
525 : : {
526 : 741 : SlabContext *slab = (SlabContext *) context;
527 : :
528 : : /*
529 : : * Check that the chunk pointer is actually somewhere on the block and is
530 : : * aligned as expected.
531 : : */
532 [ + - ]: 741 : Assert(chunk >= SlabBlockGetChunk(slab, block, 0));
533 [ + - ]: 741 : Assert(chunk <= SlabBlockGetChunk(slab, block, slab->chunksPerBlock - 1));
534 [ + - ]: 741 : Assert(SlabChunkMod(slab, block, chunk) == 0);
535 : :
536 : : /* Prepare to initialize the chunk header. */
537 : 741 : VALGRIND_MAKE_MEM_UNDEFINED(chunk, Slab_CHUNKHDRSZ);
538 : :
539 : 741 : MemoryChunkSetHdrMask(chunk, block, MAXALIGN(slab->chunkSize), MCTX_SLAB_ID);
540 : :
541 : : #ifdef MEMORY_CONTEXT_CHECKING
542 : : /* slab mark to catch clobber of "unused" space */
543 [ + - ]: 741 : Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
544 : 741 : set_sentinel(MemoryChunkGetPointer(chunk), size);
545 : 741 : VALGRIND_MAKE_MEM_NOACCESS(((char *) chunk) + Slab_CHUNKHDRSZ +
546 : : slab->chunkSize,
547 : : slab->fullChunkSize -
548 : : (slab->chunkSize + Slab_CHUNKHDRSZ));
549 : : #endif
550 : :
551 : : #ifdef RANDOMIZE_ALLOCATED_MEMORY
552 : : /* fill the allocated space with junk */
553 : : randomize_mem((char *) MemoryChunkGetPointer(chunk), size);
554 : : #endif
555 : :
556 : : /* Disallow access to the chunk header. */
557 : 741 : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
558 : :
559 : 1482 : return MemoryChunkGetPointer(chunk);
560 : 741 : }
561 : :
562 : : pg_noinline
563 : : static void *
564 : 740 : SlabAllocFromNewBlock(MemoryContext context, Size size, int flags)
565 : : {
566 : 740 : SlabContext *slab = (SlabContext *) context;
567 : 740 : SlabBlock *block;
568 : 740 : MemoryChunk *chunk;
569 : 740 : dlist_head *blocklist;
570 : 740 : int blocklist_idx;
571 : :
572 : : /* to save allocating a new one, first check the empty blocks list */
573 [ + + ]: 740 : if (dclist_count(&slab->emptyblocks) > 0)
574 : : {
575 : 4 : dlist_node *node = dclist_pop_head_node(&slab->emptyblocks);
576 : :
577 : 4 : block = dlist_container(SlabBlock, node, node);
578 : :
579 : : /*
580 : : * SlabFree() should have left this block in a valid state with all
581 : : * chunks free. Ensure that's the case.
582 : : */
583 [ + - ]: 4 : Assert(block->nfree == slab->chunksPerBlock);
584 : :
585 : : /* fetch the next chunk from this block */
586 : 4 : chunk = SlabGetNextFreeChunk(slab, block);
587 : 4 : }
588 : : else
589 : : {
590 : 736 : block = (SlabBlock *) malloc(slab->blockSize);
591 : :
592 [ - + ]: 736 : if (unlikely(block == NULL))
593 : 0 : return MemoryContextAllocationFailure(context, size, flags);
594 : :
595 : : /* Make a vchunk covering the new block's header */
596 : 736 : VALGRIND_MEMPOOL_ALLOC(slab, block, Slab_BLOCKHDRSZ);
597 : :
598 : 736 : block->slab = slab;
599 : 736 : context->mem_allocated += slab->blockSize;
600 : :
601 : : /* use the first chunk in the new block */
602 : 736 : chunk = SlabBlockGetChunk(slab, block, 0);
603 : :
604 : 736 : block->nfree = slab->chunksPerBlock - 1;
605 : 736 : block->unused = SlabBlockGetChunk(slab, block, 1);
606 : 736 : block->freehead = NULL;
607 : 736 : block->nunused = slab->chunksPerBlock - 1;
608 : : }
609 : :
610 : : /* find the blocklist element for storing blocks with 1 used chunk */
611 : 740 : blocklist_idx = SlabBlocklistIndex(slab, block->nfree);
612 : 740 : blocklist = &slab->blocklist[blocklist_idx];
613 : :
614 : : /* this better be empty. We just added a block thinking it was */
615 [ + - ]: 740 : Assert(dlist_is_empty(blocklist));
616 : :
617 : 740 : dlist_push_head(blocklist, &block->node);
618 : :
619 : 740 : slab->curBlocklistIndex = blocklist_idx;
620 : :
621 : 740 : return SlabAllocSetupNewChunk(context, block, chunk, size);
622 : 740 : }
623 : :
624 : : /*
625 : : * SlabAllocInvalidSize
626 : : * Handle raising an ERROR for an invalid size request. We don't do this
627 : : * in slab alloc as calling the elog functions would force the compiler
628 : : * to setup the stack frame in SlabAlloc. For performance reasons, we
629 : : * want to avoid that.
630 : : */
631 : : pg_noinline
632 : : pg_noreturn
633 : : static void
634 : 0 : SlabAllocInvalidSize(MemoryContext context, Size size)
635 : : {
636 : 0 : SlabContext *slab = (SlabContext *) context;
637 : :
638 [ # # # # ]: 0 : elog(ERROR, "unexpected alloc chunk size %zu (expected %u)", size,
639 : : slab->chunkSize);
640 : 0 : }
641 : :
642 : : /*
643 : : * SlabAlloc
644 : : * Returns a pointer to a newly allocated memory chunk or raises an ERROR
645 : : * on allocation failure, or returns NULL when flags contains
646 : : * MCXT_ALLOC_NO_OOM. 'size' must be the same size as was specified
647 : : * during SlabContextCreate().
648 : : *
649 : : * This function should only contain the most common code paths. Everything
650 : : * else should be in pg_noinline helper functions, thus avoiding the overhead
651 : : * of creating a stack frame for the common cases. Allocating memory is often
652 : : * a bottleneck in many workloads, so avoiding stack frame setup is
653 : : * worthwhile. Helper functions should always directly return the newly
654 : : * allocated memory so that we can just return that address directly as a tail
655 : : * call.
656 : : */
657 : : void *
658 : 741 : SlabAlloc(MemoryContext context, Size size, int flags)
659 : : {
660 : 741 : SlabContext *slab = (SlabContext *) context;
661 : 741 : SlabBlock *block;
662 : 741 : MemoryChunk *chunk;
663 : :
664 [ + - ]: 741 : Assert(SlabIsValid(slab));
665 : :
666 : : /* sanity check that this is pointing to a valid blocklist */
667 [ + - ]: 741 : Assert(slab->curBlocklistIndex >= 0);
668 [ + - ]: 741 : Assert(slab->curBlocklistIndex <= SlabBlocklistIndex(slab, slab->chunksPerBlock));
669 : :
670 : : /*
671 : : * Make sure we only allow correct request size. This doubles as the
672 : : * MemoryContextCheckSize check.
673 : : */
674 [ + - ]: 741 : if (unlikely(size != slab->chunkSize))
675 : 0 : SlabAllocInvalidSize(context, size);
676 : :
677 [ + + ]: 741 : if (unlikely(slab->curBlocklistIndex == 0))
678 : : {
679 : : /*
680 : : * Handle the case when there are no partially filled blocks
681 : : * available. This happens either when the last allocation took the
682 : : * last chunk in the block, or when SlabFree() free'd the final block.
683 : : */
684 : 740 : return SlabAllocFromNewBlock(context, size, flags);
685 : : }
686 : : else
687 : : {
688 : 1 : dlist_head *blocklist = &slab->blocklist[slab->curBlocklistIndex];
689 : 1 : int new_blocklist_idx;
690 : :
691 [ + - ]: 1 : Assert(!dlist_is_empty(blocklist));
692 : :
693 : : /* grab the block from the blocklist */
694 : 1 : block = dlist_head_element(SlabBlock, node, blocklist);
695 : :
696 : : /* make sure we actually got a valid block, with matching nfree */
697 [ + - ]: 1 : Assert(block != NULL);
698 [ + - ]: 1 : Assert(slab->curBlocklistIndex == SlabBlocklistIndex(slab, block->nfree));
699 [ + - ]: 1 : Assert(block->nfree > 0);
700 : :
701 : : /* fetch the next chunk from this block */
702 : 1 : chunk = SlabGetNextFreeChunk(slab, block);
703 : :
704 : : /* get the new blocklist index based on the new free chunk count */
705 : 1 : new_blocklist_idx = SlabBlocklistIndex(slab, block->nfree);
706 : :
707 : : /*
708 : : * Handle the case where the blocklist index changes. This also deals
709 : : * with blocks becoming full as only full blocks go at index 0.
710 : : */
711 [ + - ]: 1 : if (unlikely(slab->curBlocklistIndex != new_blocklist_idx))
712 : : {
713 : 0 : dlist_delete_from(blocklist, &block->node);
714 : 0 : dlist_push_head(&slab->blocklist[new_blocklist_idx], &block->node);
715 : :
716 [ # # ]: 0 : if (dlist_is_empty(blocklist))
717 : 0 : slab->curBlocklistIndex = SlabFindNextBlockListIndex(slab);
718 : 0 : }
719 : 1 : }
720 : :
721 : 1 : return SlabAllocSetupNewChunk(context, block, chunk, size);
722 : 741 : }
723 : :
724 : : /*
725 : : * SlabFree
726 : : * Frees allocated memory; memory is removed from the slab.
727 : : */
728 : : void
729 : 42 : SlabFree(void *pointer)
730 : : {
731 : 42 : MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
732 : 42 : SlabBlock *block;
733 : 42 : SlabContext *slab;
734 : 42 : int curBlocklistIdx;
735 : 42 : int newBlocklistIdx;
736 : :
737 : : /* Allow access to the chunk header. */
738 : 42 : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
739 : :
740 : 42 : block = MemoryChunkGetBlock(chunk);
741 : :
742 : : /*
743 : : * For speed reasons we just Assert that the referenced block is good.
744 : : * Future field experience may show that this Assert had better become a
745 : : * regular runtime test-and-elog check.
746 : : */
747 [ + - ]: 42 : Assert(SlabBlockIsValid(block));
748 : 42 : slab = block->slab;
749 : :
750 : : #ifdef MEMORY_CONTEXT_CHECKING
751 : : /* Test for someone scribbling on unused space in chunk */
752 [ + - ]: 42 : Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
753 [ + - ]: 42 : if (!sentinel_ok(pointer, slab->chunkSize))
754 [ # # # # ]: 0 : elog(WARNING, "detected write past chunk end in %s %p",
755 : : slab->header.name, chunk);
756 : : #endif
757 : :
758 : : /* push this chunk onto the head of the block's free list */
759 : 42 : *(MemoryChunk **) pointer = block->freehead;
760 : 42 : block->freehead = chunk;
761 : :
762 : 42 : block->nfree++;
763 : :
764 [ + - ]: 42 : Assert(block->nfree > 0);
765 [ + - ]: 42 : Assert(block->nfree <= slab->chunksPerBlock);
766 : :
767 : : #ifdef CLOBBER_FREED_MEMORY
768 : : /* don't wipe the free list MemoryChunk pointer stored in the chunk */
769 : 84 : wipe_mem((char *) pointer + sizeof(MemoryChunk *),
770 : 42 : slab->chunkSize - sizeof(MemoryChunk *));
771 : : #endif
772 : :
773 : 42 : curBlocklistIdx = SlabBlocklistIndex(slab, block->nfree - 1);
774 : 42 : newBlocklistIdx = SlabBlocklistIndex(slab, block->nfree);
775 : :
776 : : /*
777 : : * Check if the block needs to be moved to another element on the
778 : : * blocklist based on it now having 1 more free chunk.
779 : : */
780 [ + - ]: 42 : if (unlikely(curBlocklistIdx != newBlocklistIdx))
781 : : {
782 : : /* do the move */
783 : 0 : dlist_delete_from(&slab->blocklist[curBlocklistIdx], &block->node);
784 : 0 : dlist_push_head(&slab->blocklist[newBlocklistIdx], &block->node);
785 : :
786 : : /*
787 : : * The blocklist[curBlocklistIdx] may now be empty or we may now be
788 : : * able to use a lower-element blocklist. We'll need to redetermine
789 : : * what the slab->curBlocklistIndex is if the current blocklist was
790 : : * changed or if a lower element one was changed. We must ensure we
791 : : * use the list with the fullest block(s).
792 : : */
793 [ # # ]: 0 : if (slab->curBlocklistIndex >= curBlocklistIdx)
794 : : {
795 : 0 : slab->curBlocklistIndex = SlabFindNextBlockListIndex(slab);
796 : :
797 : : /*
798 : : * We know there must be a block with at least 1 unused chunk as
799 : : * we just pfree'd one. Ensure curBlocklistIndex reflects this.
800 : : */
801 [ # # ]: 0 : Assert(slab->curBlocklistIndex > 0);
802 : 0 : }
803 : 0 : }
804 : :
805 : : /* Handle when a block becomes completely empty */
806 [ + + ]: 42 : if (unlikely(block->nfree == slab->chunksPerBlock))
807 : : {
808 : : /* remove the block */
809 : 41 : dlist_delete_from(&slab->blocklist[newBlocklistIdx], &block->node);
810 : :
811 : : /*
812 : : * To avoid thrashing malloc/free, we keep a list of empty blocks that
813 : : * we can reuse again instead of having to malloc a new one.
814 : : */
815 [ + - ]: 41 : if (dclist_count(&slab->emptyblocks) < SLAB_MAXIMUM_EMPTY_BLOCKS)
816 : 41 : dclist_push_head(&slab->emptyblocks, &block->node);
817 : : else
818 : : {
819 : : /*
820 : : * When we have enough empty blocks stored already, we actually
821 : : * free the block.
822 : : */
823 : : #ifdef CLOBBER_FREED_MEMORY
824 : 0 : wipe_mem(block, slab->blockSize);
825 : : #endif
826 : :
827 : : /* As in aset.c, free block-header vchunks explicitly */
828 : 0 : VALGRIND_MEMPOOL_FREE(slab, block);
829 : :
830 : 0 : free(block);
831 : 0 : slab->header.mem_allocated -= slab->blockSize;
832 : : }
833 : :
834 : : /*
835 : : * Check if we need to reset the blocklist index. This is required
836 : : * when the blocklist this block is on has become completely empty.
837 : : */
838 [ + - - + ]: 41 : if (slab->curBlocklistIndex == newBlocklistIdx &&
839 : 41 : dlist_is_empty(&slab->blocklist[newBlocklistIdx]))
840 : 41 : slab->curBlocklistIndex = SlabFindNextBlockListIndex(slab);
841 : 41 : }
842 : 42 : }
843 : :
844 : : /*
845 : : * SlabRealloc
846 : : * Change the allocated size of a chunk.
847 : : *
848 : : * As Slab is designed for allocating equally-sized chunks of memory, it can't
849 : : * do an actual chunk size change. We try to be gentle and allow calls with
850 : : * exactly the same size, as in that case we can simply return the same
851 : : * chunk. When the size differs, we throw an error.
852 : : *
853 : : * We could also allow requests with size < chunkSize. That however seems
854 : : * rather pointless - Slab is meant for chunks of constant size, and moreover
855 : : * realloc is usually used to enlarge the chunk.
856 : : */
857 : : void *
858 : 0 : SlabRealloc(void *pointer, Size size, int flags)
859 : : {
860 : 0 : MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
861 : 0 : SlabBlock *block;
862 : 0 : SlabContext *slab;
863 : :
864 : : /* Allow access to the chunk header. */
865 : 0 : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
866 : :
867 : 0 : block = MemoryChunkGetBlock(chunk);
868 : :
869 : : /* Disallow access to the chunk header. */
870 : 0 : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
871 : :
872 : : /*
873 : : * Try to verify that we have a sane block pointer: the block header
874 : : * should reference a slab context. (We use a test-and-elog, not just
875 : : * Assert, because it seems highly likely that we're here in error in the
876 : : * first place.)
877 : : */
878 [ # # ]: 0 : if (!SlabBlockIsValid(block))
879 [ # # # # ]: 0 : elog(ERROR, "could not find block containing chunk %p", chunk);
880 : 0 : slab = block->slab;
881 : :
882 : : /* can't do actual realloc with slab, but let's try to be gentle */
883 [ # # ]: 0 : if (size == slab->chunkSize)
884 : 0 : return pointer;
885 : :
886 [ # # # # ]: 0 : elog(ERROR, "slab allocator does not support realloc()");
887 : 0 : return NULL; /* keep compiler quiet */
888 : 0 : }
889 : :
890 : : /*
891 : : * SlabGetChunkContext
892 : : * Return the MemoryContext that 'pointer' belongs to.
893 : : */
894 : : MemoryContext
895 : 0 : SlabGetChunkContext(void *pointer)
896 : : {
897 : 0 : MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
898 : 0 : SlabBlock *block;
899 : :
900 : : /* Allow access to the chunk header. */
901 : 0 : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
902 : :
903 : 0 : block = MemoryChunkGetBlock(chunk);
904 : :
905 : : /* Disallow access to the chunk header. */
906 : 0 : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
907 : :
908 [ # # ]: 0 : Assert(SlabBlockIsValid(block));
909 : :
910 : 0 : return &block->slab->header;
911 : 0 : }
912 : :
913 : : /*
914 : : * SlabGetChunkSpace
915 : : * Given a currently-allocated chunk, determine the total space
916 : : * it occupies (including all memory-allocation overhead).
917 : : */
918 : : Size
919 : 0 : SlabGetChunkSpace(void *pointer)
920 : : {
921 : 0 : MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
922 : 0 : SlabBlock *block;
923 : 0 : SlabContext *slab;
924 : :
925 : : /* Allow access to the chunk header. */
926 : 0 : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
927 : :
928 : 0 : block = MemoryChunkGetBlock(chunk);
929 : :
930 : : /* Disallow access to the chunk header. */
931 : 0 : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
932 : :
933 [ # # ]: 0 : Assert(SlabBlockIsValid(block));
934 : 0 : slab = block->slab;
935 : :
936 : 0 : return slab->fullChunkSize;
937 : 0 : }
938 : :
939 : : /*
940 : : * SlabIsEmpty
941 : : * Is the slab empty of any allocated space?
942 : : */
943 : : bool
944 : 0 : SlabIsEmpty(MemoryContext context)
945 : : {
946 [ # # ]: 0 : Assert(SlabIsValid((SlabContext *) context));
947 : :
948 : 0 : return (context->mem_allocated == 0);
949 : : }
950 : :
951 : : /*
952 : : * SlabStats
953 : : * Compute stats about memory consumption of a Slab context.
954 : : *
955 : : * printfunc: if not NULL, pass a human-readable stats string to this.
956 : : * passthru: pass this pointer through to printfunc.
957 : : * totals: if not NULL, add stats about this context into *totals.
958 : : * print_to_stderr: print stats to stderr if true, elog otherwise.
959 : : */
960 : : void
961 : 0 : SlabStats(MemoryContext context,
962 : : MemoryStatsPrintFunc printfunc, void *passthru,
963 : : MemoryContextCounters *totals,
964 : : bool print_to_stderr)
965 : : {
966 : 0 : SlabContext *slab = (SlabContext *) context;
967 : 0 : Size nblocks = 0;
968 : 0 : Size freechunks = 0;
969 : 0 : Size totalspace;
970 : 0 : Size freespace = 0;
971 : 0 : int i;
972 : :
973 [ # # ]: 0 : Assert(SlabIsValid(slab));
974 : :
975 : : /* Include context header in totalspace */
976 : 0 : totalspace = Slab_CONTEXT_HDRSZ(slab->chunksPerBlock);
977 : :
978 : : /* Add the space consumed by blocks in the emptyblocks list */
979 : 0 : totalspace += dclist_count(&slab->emptyblocks) * slab->blockSize;
980 : :
981 [ # # ]: 0 : for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
982 : : {
983 : 0 : dlist_iter iter;
984 : :
985 [ # # # # ]: 0 : dlist_foreach(iter, &slab->blocklist[i])
986 : : {
987 : 0 : SlabBlock *block = dlist_container(SlabBlock, node, iter.cur);
988 : :
989 : 0 : nblocks++;
990 : 0 : totalspace += slab->blockSize;
991 : 0 : freespace += slab->fullChunkSize * block->nfree;
992 : 0 : freechunks += block->nfree;
993 : 0 : }
994 : 0 : }
995 : :
996 [ # # ]: 0 : if (printfunc)
997 : : {
998 : 0 : char stats_string[200];
999 : :
1000 : : /* XXX should we include free chunks on empty blocks? */
1001 : 0 : snprintf(stats_string, sizeof(stats_string),
1002 : : "%zu total in %zu blocks; %u empty blocks; %zu free (%zu chunks); %zu used",
1003 : 0 : totalspace, nblocks, dclist_count(&slab->emptyblocks),
1004 : 0 : freespace, freechunks, totalspace - freespace);
1005 : 0 : printfunc(context, passthru, stats_string, print_to_stderr);
1006 : 0 : }
1007 : :
1008 [ # # ]: 0 : if (totals)
1009 : : {
1010 : 0 : totals->nblocks += nblocks;
1011 : 0 : totals->freechunks += freechunks;
1012 : 0 : totals->totalspace += totalspace;
1013 : 0 : totals->freespace += freespace;
1014 : 0 : }
1015 : 0 : }
1016 : :
1017 : :
1018 : : #ifdef MEMORY_CONTEXT_CHECKING
1019 : :
1020 : : /*
1021 : : * SlabCheck
1022 : : * Walk through all blocks looking for inconsistencies.
1023 : : *
1024 : : * NOTE: report errors as WARNING, *not* ERROR or FATAL. Otherwise you'll
1025 : : * find yourself in an infinite loop when trouble occurs, because this
1026 : : * routine will be entered again when elog cleanup tries to release memory!
1027 : : */
1028 : : void
1029 : 3485 : SlabCheck(MemoryContext context)
1030 : : {
1031 : 3485 : SlabContext *slab = (SlabContext *) context;
1032 : 3485 : int i;
1033 : 3485 : int nblocks = 0;
1034 : 3485 : const char *name = slab->header.name;
1035 : 3485 : dlist_iter iter;
1036 : :
1037 [ + - ]: 3485 : Assert(SlabIsValid(slab));
1038 [ + - ]: 3485 : Assert(slab->chunksPerBlock > 0);
1039 : :
1040 : : /*
1041 : : * Have a look at the empty blocks. These should have all their chunks
1042 : : * marked as free. Ensure that's the case.
1043 : : */
1044 [ + - + + ]: 3522 : dclist_foreach(iter, &slab->emptyblocks)
1045 : : {
1046 : 37 : SlabBlock *block = dlist_container(SlabBlock, node, iter.cur);
1047 : :
1048 [ + - ]: 37 : if (block->nfree != slab->chunksPerBlock)
1049 [ # # # # ]: 0 : elog(WARNING, "problem in slab %s: empty block %p should have %d free chunks but has %d chunks free",
1050 : : name, block, slab->chunksPerBlock, block->nfree);
1051 : 37 : }
1052 : :
1053 : : /* walk the non-empty block lists */
1054 [ + + ]: 13940 : for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
1055 : : {
1056 : 10455 : int j,
1057 : : nfree;
1058 : :
1059 : : /* walk all blocks on this blocklist */
1060 [ + - + + ]: 11154 : dlist_foreach(iter, &slab->blocklist[i])
1061 : : {
1062 : 699 : SlabBlock *block = dlist_container(SlabBlock, node, iter.cur);
1063 : 699 : MemoryChunk *cur_chunk;
1064 : :
1065 : : /*
1066 : : * Make sure the number of free chunks (in the block header)
1067 : : * matches the position in the blocklist.
1068 : : */
1069 [ + - ]: 699 : if (SlabBlocklistIndex(slab, block->nfree) != i)
1070 [ # # # # ]: 0 : elog(WARNING, "problem in slab %s: block %p is on blocklist %d but should be on blocklist %d",
1071 : : name, block, i, SlabBlocklistIndex(slab, block->nfree));
1072 : :
1073 : : /* make sure the block is not empty */
1074 [ + - ]: 699 : if (block->nfree >= slab->chunksPerBlock)
1075 [ # # # # ]: 0 : elog(WARNING, "problem in slab %s: empty block %p incorrectly stored on blocklist element %d",
1076 : : name, block, i);
1077 : :
1078 : : /* make sure the slab pointer correctly points to this context */
1079 [ + - ]: 699 : if (block->slab != slab)
1080 [ # # # # ]: 0 : elog(WARNING, "problem in slab %s: bogus slab link in block %p",
1081 : : name, block);
1082 : :
1083 : : /* reset the array of free chunks for this block */
1084 : 699 : memset(slab->isChunkFree, 0, (slab->chunksPerBlock * sizeof(bool)));
1085 : 699 : nfree = 0;
1086 : :
1087 : : /* walk through the block's free list chunks */
1088 : 699 : cur_chunk = block->freehead;
1089 [ + + ]: 700 : while (cur_chunk != NULL)
1090 : : {
1091 : 1 : int chunkidx = SlabChunkIndex(slab, block, cur_chunk);
1092 : :
1093 : : /*
1094 : : * Ensure the free list link points to something on the block
1095 : : * at an address aligned according to the full chunk size.
1096 : : */
1097 [ + - ]: 1 : if (cur_chunk < SlabBlockGetChunk(slab, block, 0) ||
1098 [ + - - + ]: 1 : cur_chunk > SlabBlockGetChunk(slab, block, slab->chunksPerBlock - 1) ||
1099 : 1 : SlabChunkMod(slab, block, cur_chunk) != 0)
1100 [ # # # # ]: 0 : elog(WARNING, "problem in slab %s: bogus free list link %p in block %p",
1101 : : name, cur_chunk, block);
1102 : :
1103 : : /* count the chunk and mark it free on the free chunk array */
1104 : 1 : nfree++;
1105 : 1 : slab->isChunkFree[chunkidx] = true;
1106 : :
1107 : : /* read pointer of the next free chunk */
1108 : 1 : VALGRIND_MAKE_MEM_DEFINED(MemoryChunkGetPointer(cur_chunk), sizeof(MemoryChunk *));
1109 : 1 : cur_chunk = *(MemoryChunk **) SlabChunkGetPointer(cur_chunk);
1110 : 1 : }
1111 : :
1112 : : /* check that the unused pointer matches what nunused claims */
1113 [ + - + - ]: 1398 : if (SlabBlockGetChunk(slab, block, slab->chunksPerBlock - block->nunused) !=
1114 : 699 : block->unused)
1115 [ # # # # ]: 0 : elog(WARNING, "problem in slab %s: mismatch detected between nunused chunks and unused pointer in block %p",
1116 : : name, block);
1117 : :
1118 : : /*
1119 : : * count the remaining free chunks that have yet to make it onto
1120 : : * the block's free list.
1121 : : */
1122 : 699 : cur_chunk = block->unused;
1123 [ + + ]: 87035 : for (j = 0; j < block->nunused; j++)
1124 : : {
1125 : 86336 : int chunkidx = SlabChunkIndex(slab, block, cur_chunk);
1126 : :
1127 : :
1128 : : /* count the chunk as free and mark it as so in the array */
1129 : 86336 : nfree++;
1130 [ - + ]: 86336 : if (chunkidx < slab->chunksPerBlock)
1131 : 86336 : slab->isChunkFree[chunkidx] = true;
1132 : :
1133 : : /* move forward 1 chunk */
1134 : 86336 : cur_chunk = (MemoryChunk *) (((char *) cur_chunk) + slab->fullChunkSize);
1135 : 86336 : }
1136 : :
1137 [ + + ]: 87735 : for (j = 0; j < slab->chunksPerBlock; j++)
1138 : : {
1139 [ + + ]: 87036 : if (!slab->isChunkFree[j])
1140 : : {
1141 : 699 : MemoryChunk *chunk = SlabBlockGetChunk(slab, block, j);
1142 : 699 : SlabBlock *chunkblock;
1143 : :
1144 : : /* Allow access to the chunk header. */
1145 : 699 : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
1146 : :
1147 : 699 : chunkblock = (SlabBlock *) MemoryChunkGetBlock(chunk);
1148 : :
1149 : : /* Disallow access to the chunk header. */
1150 : 699 : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
1151 : :
1152 : : /*
1153 : : * check the chunk's blockoffset correctly points back to
1154 : : * the block
1155 : : */
1156 [ + - ]: 699 : if (chunkblock != block)
1157 [ # # # # ]: 0 : elog(WARNING, "problem in slab %s: bogus block link in block %p, chunk %p",
1158 : : name, block, chunk);
1159 : :
1160 : : /* check the sentinel byte is intact */
1161 [ - + ]: 699 : Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
1162 [ + - ]: 699 : if (!sentinel_ok(chunk, Slab_CHUNKHDRSZ + slab->chunkSize))
1163 [ # # # # ]: 0 : elog(WARNING, "problem in slab %s: detected write past chunk end in block %p, chunk %p",
1164 : : name, block, chunk);
1165 : 699 : }
1166 : 87036 : }
1167 : :
1168 : : /*
1169 : : * Make sure we got the expected number of free chunks (as tracked
1170 : : * in the block header).
1171 : : */
1172 [ + - ]: 699 : if (nfree != block->nfree)
1173 [ # # # # ]: 0 : elog(WARNING, "problem in slab %s: nfree in block %p is %d but %d chunk were found as free",
1174 : : name, block, block->nfree, nfree);
1175 : :
1176 : 699 : nblocks++;
1177 : 699 : }
1178 : 10455 : }
1179 : :
1180 : : /* the stored empty blocks are tracked in mem_allocated too */
1181 : 3485 : nblocks += dclist_count(&slab->emptyblocks);
1182 : :
1183 [ + - ]: 3485 : Assert(nblocks * slab->blockSize == context->mem_allocated);
1184 : 3485 : }
1185 : :
1186 : : #endif /* MEMORY_CONTEXT_CHECKING */
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