1 /*-------------------------------------------------------------------------
2 *
3 * bufmgr.h
4 * POSTGRES buffer manager definitions.
5 *
6 *
7 * Portions Copyright (c) 1996-2020, 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 "storage/block.h"
18 #include "storage/buf.h"
19 #include "storage/bufpage.h"
20 #include "storage/relfilenode.h"
21 #include "utils/relcache.h"
22 #include "utils/snapmgr.h"
23
24 typedef void *Block;
25
26 /* Possible arguments for GetAccessStrategy() */
27 typedef enum BufferAccessStrategyType
28 {
29 BAS_NORMAL, /* Normal random access */
30 BAS_BULKREAD, /* Large read-only scan (hint bit updates are
31 * ok) */
32 BAS_BULKWRITE, /* Large multi-block write (e.g. COPY IN) */
33 BAS_VACUUM /* VACUUM */
34 } BufferAccessStrategyType;
35
36 /* Possible modes for ReadBufferExtended() */
37 typedef enum
38 {
39 RBM_NORMAL, /* Normal read */
40 RBM_ZERO_AND_LOCK, /* Don't read from disk, caller will
41 * initialize. Also locks the page. */
42 RBM_ZERO_AND_CLEANUP_LOCK, /* Like RBM_ZERO_AND_LOCK, but locks the page
43 * in "cleanup" mode */
44 RBM_ZERO_ON_ERROR, /* Read, but return an all-zeros page on error */
45 RBM_NORMAL_NO_LOG /* Don't log page as invalid during WAL
46 * replay; otherwise same as RBM_NORMAL */
47 } ReadBufferMode;
48
49 /*
50 * Type returned by PrefetchBuffer().
51 */
52 typedef struct PrefetchBufferResult
53 {
54 Buffer recent_buffer; /* If valid, a hit (recheck needed!) */
55 bool initiated_io; /* If true, a miss resulting in async I/O */
56 } PrefetchBufferResult;
57
58 /* forward declared, to avoid having to expose buf_internals.h here */
59 struct WritebackContext;
60
61 /* forward declared, to avoid including smgr.h here */
62 struct SMgrRelationData;
63
64 /* in globals.c ... this duplicates miscadmin.h */
65 extern PGDLLIMPORT int NBuffers;
66
67 /* in bufmgr.c */
68 extern bool zero_damaged_pages;
69 extern int bgwriter_lru_maxpages;
70 extern double bgwriter_lru_multiplier;
71 extern bool track_io_timing;
72 extern int effective_io_concurrency;
73 extern int maintenance_io_concurrency;
74
75 extern int checkpoint_flush_after;
76 extern int backend_flush_after;
77 extern int bgwriter_flush_after;
78
79 /* in buf_init.c */
80 extern PGDLLIMPORT char *BufferBlocks;
81
82 /* in localbuf.c */
83 extern PGDLLIMPORT int NLocBuffer;
84 extern PGDLLIMPORT Block *LocalBufferBlockPointers;
85 extern PGDLLIMPORT int32 *LocalRefCount;
86
87 /* upper limit for effective_io_concurrency */
88 #define MAX_IO_CONCURRENCY 1000
89
90 /* special block number for ReadBuffer() */
91 #define P_NEW InvalidBlockNumber /* grow the file to get a new page */
92
93 /*
94 * Buffer content lock modes (mode argument for LockBuffer())
95 */
96 #define BUFFER_LOCK_UNLOCK 0
97 #define BUFFER_LOCK_SHARE 1
98 #define BUFFER_LOCK_EXCLUSIVE 2
99
100 /*
101 * These routines are beaten on quite heavily, hence the macroization.
102 */
103
104 /*
105 * BufferIsValid
106 * True iff the given buffer number is valid (either as a shared
107 * or local buffer).
108 *
109 * Note: For a long time this was defined the same as BufferIsPinned,
110 * that is it would say False if you didn't hold a pin on the buffer.
111 * I believe this was bogus and served only to mask logic errors.
112 * Code should always know whether it has a buffer reference,
113 * independently of the pin state.
114 *
115 * Note: For a further long time this was not quite the inverse of the
116 * BufferIsInvalid() macro, in that it also did sanity checks to verify
117 * that the buffer number was in range. Most likely, this macro was
118 * originally intended only to be used in assertions, but its use has
119 * since expanded quite a bit, and the overhead of making those checks
120 * even in non-assert-enabled builds can be significant. Thus, we've
121 * now demoted the range checks to assertions within the macro itself.
122 */
123 #define BufferIsValid(bufnum) \
124 ( \
125 AssertMacro((bufnum) <= NBuffers && (bufnum) >= -NLocBuffer), \
126 (bufnum) != InvalidBuffer \
127 )
128
129 /*
130 * BufferGetBlock
131 * Returns a reference to a disk page image associated with a buffer.
132 *
133 * Note:
134 * Assumes buffer is valid.
135 */
136 #define BufferGetBlock(buffer) \
137 ( \
138 AssertMacro(BufferIsValid(buffer)), \
139 BufferIsLocal(buffer) ? \
140 LocalBufferBlockPointers[-(buffer) - 1] \
141 : \
142 (Block) (BufferBlocks + ((Size) ((buffer) - 1)) * BLCKSZ) \
143 )
144
145 /*
146 * BufferGetPageSize
147 * Returns the page size within a buffer.
148 *
149 * Notes:
150 * Assumes buffer is valid.
151 *
152 * The buffer can be a raw disk block and need not contain a valid
153 * (formatted) disk page.
154 */
155 /* XXX should dig out of buffer descriptor */
156 #define BufferGetPageSize(buffer) \
157 ( \
158 AssertMacro(BufferIsValid(buffer)), \
159 (Size)BLCKSZ \
160 )
161
162 /*
163 * BufferGetPage
164 * Returns the page associated with a buffer.
165 *
166 * When this is called as part of a scan, there may be a need for a nearby
167 * call to TestForOldSnapshot(). See the definition of that for details.
168 */
169 #define BufferGetPage(buffer) ((Page)BufferGetBlock(buffer))
170
171 /*
172 * prototypes for functions in bufmgr.c
173 */
174 extern PrefetchBufferResult PrefetchSharedBuffer(struct SMgrRelationData *smgr_reln,
175 ForkNumber forkNum,
176 BlockNumber blockNum);
177 extern PrefetchBufferResult PrefetchBuffer(Relation reln, ForkNumber forkNum,
178 BlockNumber blockNum);
179 extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
180 extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum,
181 BlockNumber blockNum, ReadBufferMode mode,
182 BufferAccessStrategy strategy);
183 extern Buffer ReadBufferWithoutRelcache(RelFileNode rnode,
184 ForkNumber forkNum, BlockNumber blockNum,
185 ReadBufferMode mode, BufferAccessStrategy strategy);
186 extern void ReleaseBuffer(Buffer buffer);
187 extern void UnlockReleaseBuffer(Buffer buffer);
188 extern void MarkBufferDirty(Buffer buffer);
189 extern void IncrBufferRefCount(Buffer buffer);
190 extern Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation,
191 BlockNumber blockNum);
192
193 extern void InitBufferPool(void);
194 extern void InitBufferPoolAccess(void);
195 extern void InitBufferPoolBackend(void);
196 extern void AtEOXact_Buffers(bool isCommit);
197 extern void PrintBufferLeakWarning(Buffer buffer);
198 extern void CheckPointBuffers(int flags);
199 extern BlockNumber BufferGetBlockNumber(Buffer buffer);
200 extern BlockNumber RelationGetNumberOfBlocksInFork(Relation relation,
201 ForkNumber forkNum);
202 extern void FlushOneBuffer(Buffer buffer);
203 extern void FlushRelationBuffers(Relation rel);
204 extern void FlushRelationsAllBuffers(struct SMgrRelationData **smgrs, int nrels);
205 extern void FlushDatabaseBuffers(Oid dbid);
206 extern void DropRelFileNodeBuffers(RelFileNodeBackend rnode, ForkNumber *forkNum,
207 int nforks, BlockNumber *firstDelBlock);
208 extern void DropRelFileNodesAllBuffers(RelFileNodeBackend *rnodes, int nnodes);
209 extern void DropDatabaseBuffers(Oid dbid);
210
211 #define RelationGetNumberOfBlocks(reln) \
212 RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM)
213
214 extern bool BufferIsPermanent(Buffer buffer);
215 extern XLogRecPtr BufferGetLSNAtomic(Buffer buffer);
216
217 #ifdef NOT_USED
218 extern void PrintPinnedBufs(void);
219 #endif
220 extern Size BufferShmemSize(void);
221 extern void BufferGetTag(Buffer buffer, RelFileNode *rnode,
222 ForkNumber *forknum, BlockNumber *blknum);
223
224 extern void MarkBufferDirtyHint(Buffer buffer, bool buffer_std);
225
226 extern void UnlockBuffers(void);
227 extern void LockBuffer(Buffer buffer, int mode);
228 extern bool ConditionalLockBuffer(Buffer buffer);
229 extern void LockBufferForCleanup(Buffer buffer);
230 extern bool ConditionalLockBufferForCleanup(Buffer buffer);
231 extern bool IsBufferCleanupOK(Buffer buffer);
232 extern bool HoldingBufferPinThatDelaysRecovery(void);
233
234 extern void AbortBufferIO(void);
235
236 extern void BufmgrCommit(void);
237 extern bool BgBufferSync(struct WritebackContext *wb_context);
238
239 extern void AtProcExit_LocalBuffers(void);
240
241 extern void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation);
242
243 /* in freelist.c */
244 extern BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype);
245 extern void FreeAccessStrategy(BufferAccessStrategy strategy);
246
247
248 /* inline functions */
249
250 /*
251 * Although this header file is nominally backend-only, certain frontend
252 * programs like pg_waldump include it. For compilers that emit static
253 * inline functions even when they're unused, that leads to unsatisfied
254 * external references; hence hide these with #ifndef FRONTEND.
255 */
256
257 #ifndef FRONTEND
258
259 /*
260 * Check whether the given snapshot is too old to have safely read the given
261 * page from the given table. If so, throw a "snapshot too old" error.
262 *
263 * This test generally needs to be performed after every BufferGetPage() call
264 * that is executed as part of a scan. It is not needed for calls made for
265 * modifying the page (for example, to position to the right place to insert a
266 * new index tuple or for vacuuming). It may also be omitted where calls to
267 * lower-level functions will have already performed the test.
268 *
269 * Note that a NULL snapshot argument is allowed and causes a fast return
270 * without error; this is to support call sites which can be called from
271 * either scans or index modification areas.
272 *
273 * For best performance, keep the tests that are fastest and/or most likely to
274 * exclude a page from old snapshot testing near the front.
275 */
276 static inline void
TestForOldSnapshot(Snapshot snapshot,Relation relation,Page page)277 TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
278 {
279 Assert(relation != NULL);
280
281 if (old_snapshot_threshold >= 0
282 && (snapshot) != NULL
283 && ((snapshot)->snapshot_type == SNAPSHOT_MVCC
284 || (snapshot)->snapshot_type == SNAPSHOT_TOAST)
285 && !XLogRecPtrIsInvalid((snapshot)->lsn)
286 && PageGetLSN(page) > (snapshot)->lsn)
287 TestForOldSnapshot_impl(snapshot, relation);
288 }
289
290 #endif /* FRONTEND */
291
292 #endif /* BUFMGR_H */
293