Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * bufmgr.h
4 : * POSTGRES buffer manager definitions.
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : * src/include/storage/bufmgr.h
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 : #ifndef BUFMGR_H
15 : #define BUFMGR_H
16 :
17 : #include "port/pg_iovec.h"
18 : #include "storage/block.h"
19 : #include "storage/buf.h"
20 : #include "storage/bufpage.h"
21 : #include "storage/relfilelocator.h"
22 : #include "utils/relcache.h"
23 : #include "utils/snapmgr.h"
24 :
25 : typedef void *Block;
26 :
27 : /*
28 : * Possible arguments for GetAccessStrategy().
29 : *
30 : * If adding a new BufferAccessStrategyType, also add a new IOContext so
31 : * IO statistics using this strategy are tracked.
32 : */
33 : typedef enum BufferAccessStrategyType
34 : {
35 : BAS_NORMAL, /* Normal random access */
36 : BAS_BULKREAD, /* Large read-only scan (hint bit updates are
37 : * ok) */
38 : BAS_BULKWRITE, /* Large multi-block write (e.g. COPY IN) */
39 : BAS_VACUUM, /* VACUUM */
40 : } BufferAccessStrategyType;
41 :
42 : /* Possible modes for ReadBufferExtended() */
43 : typedef enum
44 : {
45 : RBM_NORMAL, /* Normal read */
46 : RBM_ZERO_AND_LOCK, /* Don't read from disk, caller will
47 : * initialize. Also locks the page. */
48 : RBM_ZERO_AND_CLEANUP_LOCK, /* Like RBM_ZERO_AND_LOCK, but locks the page
49 : * in "cleanup" mode */
50 : RBM_ZERO_ON_ERROR, /* Read, but return an all-zeros page on error */
51 : RBM_NORMAL_NO_LOG, /* Don't log page as invalid during WAL
52 : * replay; otherwise same as RBM_NORMAL */
53 : } ReadBufferMode;
54 :
55 : /*
56 : * Type returned by PrefetchBuffer().
57 : */
58 : typedef struct PrefetchBufferResult
59 : {
60 : Buffer recent_buffer; /* If valid, a hit (recheck needed!) */
61 : bool initiated_io; /* If true, a miss resulting in async I/O */
62 : } PrefetchBufferResult;
63 :
64 : /*
65 : * Flags influencing the behaviour of ExtendBufferedRel*
66 : */
67 : typedef enum ExtendBufferedFlags
68 : {
69 : /*
70 : * Don't acquire extension lock. This is safe only if the relation isn't
71 : * shared, an access exclusive lock is held or if this is the startup
72 : * process.
73 : */
74 : EB_SKIP_EXTENSION_LOCK = (1 << 0),
75 :
76 : /* Is this extension part of recovery? */
77 : EB_PERFORMING_RECOVERY = (1 << 1),
78 :
79 : /*
80 : * Should the fork be created if it does not currently exist? This likely
81 : * only ever makes sense for relation forks.
82 : */
83 : EB_CREATE_FORK_IF_NEEDED = (1 << 2),
84 :
85 : /* Should the first (possibly only) return buffer be returned locked? */
86 : EB_LOCK_FIRST = (1 << 3),
87 :
88 : /* Should the smgr size cache be cleared? */
89 : EB_CLEAR_SIZE_CACHE = (1 << 4),
90 :
91 : /* internal flags follow */
92 : EB_LOCK_TARGET = (1 << 5),
93 : } ExtendBufferedFlags;
94 :
95 : /*
96 : * Some functions identify relations either by relation or smgr +
97 : * relpersistence. Used via the BMR_REL()/BMR_SMGR() macros below. This
98 : * allows us to use the same function for both recovery and normal operation.
99 : */
100 : typedef struct BufferManagerRelation
101 : {
102 : Relation rel;
103 : struct SMgrRelationData *smgr;
104 : char relpersistence;
105 : } BufferManagerRelation;
106 :
107 : #define BMR_REL(p_rel) ((BufferManagerRelation){.rel = p_rel})
108 : #define BMR_SMGR(p_smgr, p_relpersistence) ((BufferManagerRelation){.smgr = p_smgr, .relpersistence = p_relpersistence})
109 :
110 : typedef enum ReadBuffersFlags
111 : {
112 : /* Zero out page if reading fails. */
113 : READ_BUFFERS_ZERO_ON_ERROR = (1 << 0),
114 :
115 : /* Call smgrprefetch() if I/O necessary. */
116 : READ_BUFFERS_ISSUE_ADVICE = (1 << 1),
117 : } ReadBuffersFlags;
118 :
119 : struct ReadBuffersOperation
120 : {
121 : /*
122 : * The following members should be set by the caller. If only smgr is
123 : * provided without rel, then smgr_persistence can be set to override the
124 : * default assumption of RELPERSISTENCE_PERMANENT.
125 : */
126 : Relation rel;
127 : struct SMgrRelationData *smgr;
128 : char smgr_persistence;
129 : ForkNumber forknum;
130 : BufferAccessStrategy strategy;
131 :
132 : /*
133 : * The following private members are private state for communication
134 : * between StartReadBuffers() and WaitReadBuffers(), initialized only if
135 : * an actual read is required, and should not be modified.
136 : */
137 : Buffer *buffers;
138 : BlockNumber blocknum;
139 : int flags;
140 : int16 nblocks;
141 : int16 io_buffers_len;
142 : };
143 :
144 : typedef struct ReadBuffersOperation ReadBuffersOperation;
145 :
146 : /* forward declared, to avoid having to expose buf_internals.h here */
147 : struct WritebackContext;
148 :
149 : /* forward declared, to avoid including smgr.h here */
150 : struct SMgrRelationData;
151 :
152 : /* in globals.c ... this duplicates miscadmin.h */
153 : extern PGDLLIMPORT int NBuffers;
154 :
155 : /* in bufmgr.c */
156 : extern PGDLLIMPORT bool zero_damaged_pages;
157 : extern PGDLLIMPORT int bgwriter_lru_maxpages;
158 : extern PGDLLIMPORT double bgwriter_lru_multiplier;
159 : extern PGDLLIMPORT bool track_io_timing;
160 :
161 : /* only applicable when prefetching is available */
162 : #ifdef USE_PREFETCH
163 : #define DEFAULT_EFFECTIVE_IO_CONCURRENCY 1
164 : #define DEFAULT_MAINTENANCE_IO_CONCURRENCY 10
165 : #else
166 : #define DEFAULT_EFFECTIVE_IO_CONCURRENCY 0
167 : #define DEFAULT_MAINTENANCE_IO_CONCURRENCY 0
168 : #endif
169 : extern PGDLLIMPORT int effective_io_concurrency;
170 : extern PGDLLIMPORT int maintenance_io_concurrency;
171 :
172 : #define MAX_IO_COMBINE_LIMIT PG_IOV_MAX
173 : #define DEFAULT_IO_COMBINE_LIMIT Min(MAX_IO_COMBINE_LIMIT, (128 * 1024) / BLCKSZ)
174 : extern PGDLLIMPORT int io_combine_limit;
175 :
176 : extern PGDLLIMPORT int checkpoint_flush_after;
177 : extern PGDLLIMPORT int backend_flush_after;
178 : extern PGDLLIMPORT int bgwriter_flush_after;
179 :
180 : /* in buf_init.c */
181 : extern PGDLLIMPORT char *BufferBlocks;
182 :
183 : /* in localbuf.c */
184 : extern PGDLLIMPORT int NLocBuffer;
185 : extern PGDLLIMPORT Block *LocalBufferBlockPointers;
186 : extern PGDLLIMPORT int32 *LocalRefCount;
187 :
188 : /* upper limit for effective_io_concurrency */
189 : #define MAX_IO_CONCURRENCY 1000
190 :
191 : /* special block number for ReadBuffer() */
192 : #define P_NEW InvalidBlockNumber /* grow the file to get a new page */
193 :
194 : /*
195 : * Buffer content lock modes (mode argument for LockBuffer())
196 : */
197 : #define BUFFER_LOCK_UNLOCK 0
198 : #define BUFFER_LOCK_SHARE 1
199 : #define BUFFER_LOCK_EXCLUSIVE 2
200 :
201 :
202 : /*
203 : * prototypes for functions in bufmgr.c
204 : */
205 : extern PrefetchBufferResult PrefetchSharedBuffer(struct SMgrRelationData *smgr_reln,
206 : ForkNumber forkNum,
207 : BlockNumber blockNum);
208 : extern PrefetchBufferResult PrefetchBuffer(Relation reln, ForkNumber forkNum,
209 : BlockNumber blockNum);
210 : extern bool ReadRecentBuffer(RelFileLocator rlocator, ForkNumber forkNum,
211 : BlockNumber blockNum, Buffer recent_buffer);
212 : extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
213 : extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum,
214 : BlockNumber blockNum, ReadBufferMode mode,
215 : BufferAccessStrategy strategy);
216 : extern Buffer ReadBufferWithoutRelcache(RelFileLocator rlocator,
217 : ForkNumber forkNum, BlockNumber blockNum,
218 : ReadBufferMode mode, BufferAccessStrategy strategy,
219 : bool permanent);
220 :
221 : extern bool StartReadBuffer(ReadBuffersOperation *operation,
222 : Buffer *buffer,
223 : BlockNumber blocknum,
224 : int flags);
225 : extern bool StartReadBuffers(ReadBuffersOperation *operation,
226 : Buffer *buffers,
227 : BlockNumber blocknum,
228 : int *nblocks,
229 : int flags);
230 : extern void WaitReadBuffers(ReadBuffersOperation *operation);
231 :
232 : extern void ReleaseBuffer(Buffer buffer);
233 : extern void UnlockReleaseBuffer(Buffer buffer);
234 : extern bool BufferIsExclusiveLocked(Buffer buffer);
235 : extern bool BufferIsDirty(Buffer buffer);
236 : extern void MarkBufferDirty(Buffer buffer);
237 : extern void IncrBufferRefCount(Buffer buffer);
238 : extern void CheckBufferIsPinnedOnce(Buffer buffer);
239 : extern Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation,
240 : BlockNumber blockNum);
241 :
242 : extern Buffer ExtendBufferedRel(BufferManagerRelation bmr,
243 : ForkNumber forkNum,
244 : BufferAccessStrategy strategy,
245 : uint32 flags);
246 : extern BlockNumber ExtendBufferedRelBy(BufferManagerRelation bmr,
247 : ForkNumber fork,
248 : BufferAccessStrategy strategy,
249 : uint32 flags,
250 : uint32 extend_by,
251 : Buffer *buffers,
252 : uint32 *extended_by);
253 : extern Buffer ExtendBufferedRelTo(BufferManagerRelation bmr,
254 : ForkNumber fork,
255 : BufferAccessStrategy strategy,
256 : uint32 flags,
257 : BlockNumber extend_to,
258 : ReadBufferMode mode);
259 :
260 : extern void InitBufferPoolAccess(void);
261 : extern void AtEOXact_Buffers(bool isCommit);
262 : extern char *DebugPrintBufferRefcount(Buffer buffer);
263 : extern void CheckPointBuffers(int flags);
264 : extern BlockNumber BufferGetBlockNumber(Buffer buffer);
265 : extern BlockNumber RelationGetNumberOfBlocksInFork(Relation relation,
266 : ForkNumber forkNum);
267 : extern void FlushOneBuffer(Buffer buffer);
268 : extern void FlushRelationBuffers(Relation rel);
269 : extern void FlushRelationsAllBuffers(struct SMgrRelationData **smgrs, int nrels);
270 : extern void CreateAndCopyRelationData(RelFileLocator src_rlocator,
271 : RelFileLocator dst_rlocator,
272 : bool permanent);
273 : extern void FlushDatabaseBuffers(Oid dbid);
274 : extern void DropRelationBuffers(struct SMgrRelationData *smgr_reln,
275 : ForkNumber *forkNum,
276 : int nforks, BlockNumber *firstDelBlock);
277 : extern void DropRelationsAllBuffers(struct SMgrRelationData **smgr_reln,
278 : int nlocators);
279 : extern void DropDatabaseBuffers(Oid dbid);
280 :
281 : #define RelationGetNumberOfBlocks(reln) \
282 : RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM)
283 :
284 : extern bool BufferIsPermanent(Buffer buffer);
285 : extern XLogRecPtr BufferGetLSNAtomic(Buffer buffer);
286 :
287 : #ifdef NOT_USED
288 : extern void PrintPinnedBufs(void);
289 : #endif
290 : extern void BufferGetTag(Buffer buffer, RelFileLocator *rlocator,
291 : ForkNumber *forknum, BlockNumber *blknum);
292 :
293 : extern void MarkBufferDirtyHint(Buffer buffer, bool buffer_std);
294 :
295 : extern void UnlockBuffers(void);
296 : extern void LockBuffer(Buffer buffer, int mode);
297 : extern bool ConditionalLockBuffer(Buffer buffer);
298 : extern void LockBufferForCleanup(Buffer buffer);
299 : extern bool ConditionalLockBufferForCleanup(Buffer buffer);
300 : extern bool IsBufferCleanupOK(Buffer buffer);
301 : extern bool HoldingBufferPinThatDelaysRecovery(void);
302 :
303 : extern bool BgBufferSync(struct WritebackContext *wb_context);
304 :
305 : extern void LimitAdditionalPins(uint32 *additional_pins);
306 : extern void LimitAdditionalLocalPins(uint32 *additional_pins);
307 :
308 : extern bool EvictUnpinnedBuffer(Buffer buf);
309 :
310 : /* in buf_init.c */
311 : extern void InitBufferPool(void);
312 : extern Size BufferShmemSize(void);
313 :
314 : /* in localbuf.c */
315 : extern void AtProcExit_LocalBuffers(void);
316 :
317 : /* in freelist.c */
318 :
319 : extern BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype);
320 : extern BufferAccessStrategy GetAccessStrategyWithSize(BufferAccessStrategyType btype,
321 : int ring_size_kb);
322 : extern int GetAccessStrategyBufferCount(BufferAccessStrategy strategy);
323 : extern int GetAccessStrategyPinLimit(BufferAccessStrategy strategy);
324 :
325 : extern void FreeAccessStrategy(BufferAccessStrategy strategy);
326 :
327 :
328 : /* inline functions */
329 :
330 : /*
331 : * Although this header file is nominally backend-only, certain frontend
332 : * programs like pg_waldump include it. For compilers that emit static
333 : * inline functions even when they're unused, that leads to unsatisfied
334 : * external references; hence hide these with #ifndef FRONTEND.
335 : */
336 :
337 : #ifndef FRONTEND
338 :
339 : /*
340 : * BufferIsValid
341 : * True iff the given buffer number is valid (either as a shared
342 : * or local buffer).
343 : *
344 : * Note: For a long time this was defined the same as BufferIsPinned,
345 : * that is it would say False if you didn't hold a pin on the buffer.
346 : * I believe this was bogus and served only to mask logic errors.
347 : * Code should always know whether it has a buffer reference,
348 : * independently of the pin state.
349 : *
350 : * Note: For a further long time this was not quite the inverse of the
351 : * BufferIsInvalid() macro, in that it also did sanity checks to verify
352 : * that the buffer number was in range. Most likely, this macro was
353 : * originally intended only to be used in assertions, but its use has
354 : * since expanded quite a bit, and the overhead of making those checks
355 : * even in non-assert-enabled builds can be significant. Thus, we've
356 : * now demoted the range checks to assertions within the macro itself.
357 : */
358 : static inline bool
359 508288888 : BufferIsValid(Buffer bufnum)
360 : {
361 : Assert(bufnum <= NBuffers);
362 : Assert(bufnum >= -NLocBuffer);
363 :
364 508288888 : return bufnum != InvalidBuffer;
365 : }
366 :
367 : /*
368 : * BufferGetBlock
369 : * Returns a reference to a disk page image associated with a buffer.
370 : *
371 : * Note:
372 : * Assumes buffer is valid.
373 : */
374 : static inline Block
375 596199516 : BufferGetBlock(Buffer buffer)
376 : {
377 : Assert(BufferIsValid(buffer));
378 :
379 596199516 : if (BufferIsLocal(buffer))
380 20057946 : return LocalBufferBlockPointers[-buffer - 1];
381 : else
382 576141570 : return (Block) (BufferBlocks + ((Size) (buffer - 1)) * BLCKSZ);
383 : }
384 :
385 : /*
386 : * BufferGetPageSize
387 : * Returns the page size within a buffer.
388 : *
389 : * Notes:
390 : * Assumes buffer is valid.
391 : *
392 : * The buffer can be a raw disk block and need not contain a valid
393 : * (formatted) disk page.
394 : */
395 : /* XXX should dig out of buffer descriptor */
396 : static inline Size
397 407018 : BufferGetPageSize(Buffer buffer)
398 : {
399 : AssertMacro(BufferIsValid(buffer));
400 407018 : return (Size) BLCKSZ;
401 : }
402 :
403 : /*
404 : * BufferGetPage
405 : * Returns the page associated with a buffer.
406 : */
407 : static inline Page
408 593976740 : BufferGetPage(Buffer buffer)
409 : {
410 593976740 : return (Page) BufferGetBlock(buffer);
411 : }
412 :
413 : #endif /* FRONTEND */
414 :
415 : #endif /* BUFMGR_H */
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