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1 : /*-------------------------------------------------------------------------
2 : *
3 : * bufmgr.h
4 : * POSTGRES buffer manager definitions.
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2017, 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 : #include "utils/tqual.h"
24 :
25 : typedef void *Block;
26 :
27 : /* Possible arguments for GetAccessStrategy() */
28 : typedef enum BufferAccessStrategyType
29 : {
30 : BAS_NORMAL, /* Normal random access */
31 : BAS_BULKREAD, /* Large read-only scan (hint bit updates are
32 : * ok) */
33 : BAS_BULKWRITE, /* Large multi-block write (e.g. COPY IN) */
34 : BAS_VACUUM /* VACUUM */
35 : } BufferAccessStrategyType;
36 :
37 : /* Possible modes for ReadBufferExtended() */
38 : typedef enum
39 : {
40 : RBM_NORMAL, /* Normal read */
41 : RBM_ZERO_AND_LOCK, /* Don't read from disk, caller will
42 : * initialize. Also locks the page. */
43 : RBM_ZERO_AND_CLEANUP_LOCK, /* Like RBM_ZERO_AND_LOCK, but locks the page
44 : * in "cleanup" mode */
45 : RBM_ZERO_ON_ERROR, /* Read, but return an all-zeros page on error */
46 : RBM_NORMAL_NO_LOG /* Don't log page as invalid during WAL
47 : * replay; otherwise same as RBM_NORMAL */
48 : } ReadBufferMode;
49 :
50 : /* forward declared, to avoid having to expose buf_internals.h here */
51 : struct WritebackContext;
52 :
53 : /* in globals.c ... this duplicates miscadmin.h */
54 : extern PGDLLIMPORT int NBuffers;
55 :
56 : /* in bufmgr.c */
57 : extern bool zero_damaged_pages;
58 : extern int bgwriter_lru_maxpages;
59 : extern double bgwriter_lru_multiplier;
60 : extern bool track_io_timing;
61 : extern int target_prefetch_pages;
62 :
63 : extern int checkpoint_flush_after;
64 : extern int backend_flush_after;
65 : extern int bgwriter_flush_after;
66 :
67 : /* in buf_init.c */
68 : extern PGDLLIMPORT char *BufferBlocks;
69 :
70 : /* in guc.c */
71 : extern int effective_io_concurrency;
72 :
73 : /* in localbuf.c */
74 : extern PGDLLIMPORT int NLocBuffer;
75 : extern PGDLLIMPORT Block *LocalBufferBlockPointers;
76 : extern PGDLLIMPORT int32 *LocalRefCount;
77 :
78 : /* upper limit for effective_io_concurrency */
79 : #define MAX_IO_CONCURRENCY 1000
80 :
81 : /* special block number for ReadBuffer() */
82 : #define P_NEW InvalidBlockNumber /* grow the file to get a new page */
83 :
84 : /*
85 : * Buffer content lock modes (mode argument for LockBuffer())
86 : */
87 : #define BUFFER_LOCK_UNLOCK 0
88 : #define BUFFER_LOCK_SHARE 1
89 : #define BUFFER_LOCK_EXCLUSIVE 2
90 :
91 : /*
92 : * These routines are beaten on quite heavily, hence the macroization.
93 : */
94 :
95 : /*
96 : * BufferIsValid
97 : * True iff the given buffer number is valid (either as a shared
98 : * or local buffer).
99 : *
100 : * Note: For a long time this was defined the same as BufferIsPinned,
101 : * that is it would say False if you didn't hold a pin on the buffer.
102 : * I believe this was bogus and served only to mask logic errors.
103 : * Code should always know whether it has a buffer reference,
104 : * independently of the pin state.
105 : *
106 : * Note: For a further long time this was not quite the inverse of the
107 : * BufferIsInvalid() macro, in that it also did sanity checks to verify
108 : * that the buffer number was in range. Most likely, this macro was
109 : * originally intended only to be used in assertions, but its use has
110 : * since expanded quite a bit, and the overhead of making those checks
111 : * even in non-assert-enabled builds can be significant. Thus, we've
112 : * now demoted the range checks to assertions within the macro itself.
113 : */
114 : #define BufferIsValid(bufnum) \
115 : ( \
116 : AssertMacro((bufnum) <= NBuffers && (bufnum) >= -NLocBuffer), \
117 : (bufnum) != InvalidBuffer \
118 : )
119 :
120 : /*
121 : * BufferGetBlock
122 : * Returns a reference to a disk page image associated with a buffer.
123 : *
124 : * Note:
125 : * Assumes buffer is valid.
126 : */
127 : #define BufferGetBlock(buffer) \
128 : ( \
129 : AssertMacro(BufferIsValid(buffer)), \
130 : BufferIsLocal(buffer) ? \
131 : LocalBufferBlockPointers[-(buffer) - 1] \
132 : : \
133 : (Block) (BufferBlocks + ((Size) ((buffer) - 1)) * BLCKSZ) \
134 : )
135 :
136 : /*
137 : * BufferGetPageSize
138 : * Returns the page size within a buffer.
139 : *
140 : * Notes:
141 : * Assumes buffer is valid.
142 : *
143 : * The buffer can be a raw disk block and need not contain a valid
144 : * (formatted) disk page.
145 : */
146 : /* XXX should dig out of buffer descriptor */
147 : #define BufferGetPageSize(buffer) \
148 : ( \
149 : AssertMacro(BufferIsValid(buffer)), \
150 : (Size)BLCKSZ \
151 : )
152 :
153 : /*
154 : * BufferGetPage
155 : * Returns the page associated with a buffer.
156 : *
157 : * When this is called as part of a scan, there may be a need for a nearby
158 : * call to TestForOldSnapshot(). See the definition of that for details.
159 : */
160 : #define BufferGetPage(buffer) ((Page)BufferGetBlock(buffer))
161 :
162 : /*
163 : * prototypes for functions in bufmgr.c
164 : */
165 : extern bool ComputeIoConcurrency(int io_concurrency, double *target);
166 : extern void PrefetchBuffer(Relation reln, ForkNumber forkNum,
167 : BlockNumber blockNum);
168 : extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
169 : extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum,
170 : BlockNumber blockNum, ReadBufferMode mode,
171 : BufferAccessStrategy strategy);
172 : extern Buffer ReadBufferWithoutRelcache(RelFileNode rnode,
173 : ForkNumber forkNum, BlockNumber blockNum,
174 : ReadBufferMode mode, BufferAccessStrategy strategy);
175 : extern void ReleaseBuffer(Buffer buffer);
176 : extern void UnlockReleaseBuffer(Buffer buffer);
177 : extern void MarkBufferDirty(Buffer buffer);
178 : extern void IncrBufferRefCount(Buffer buffer);
179 : extern Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation,
180 : BlockNumber blockNum);
181 :
182 : extern void InitBufferPool(void);
183 : extern void InitBufferPoolAccess(void);
184 : extern void InitBufferPoolBackend(void);
185 : extern void AtEOXact_Buffers(bool isCommit);
186 : extern void PrintBufferLeakWarning(Buffer buffer);
187 : extern void CheckPointBuffers(int flags);
188 : extern BlockNumber BufferGetBlockNumber(Buffer buffer);
189 : extern BlockNumber RelationGetNumberOfBlocksInFork(Relation relation,
190 : ForkNumber forkNum);
191 : extern void FlushOneBuffer(Buffer buffer);
192 : extern void FlushRelationBuffers(Relation rel);
193 : extern void FlushDatabaseBuffers(Oid dbid);
194 : extern void DropRelFileNodeBuffers(RelFileNodeBackend rnode,
195 : ForkNumber forkNum, BlockNumber firstDelBlock);
196 : extern void DropRelFileNodesAllBuffers(RelFileNodeBackend *rnodes, int nnodes);
197 : extern void DropDatabaseBuffers(Oid dbid);
198 :
199 : #define RelationGetNumberOfBlocks(reln) \
200 : RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM)
201 :
202 : extern bool BufferIsPermanent(Buffer buffer);
203 : extern XLogRecPtr BufferGetLSNAtomic(Buffer buffer);
204 :
205 : #ifdef NOT_USED
206 : extern void PrintPinnedBufs(void);
207 : #endif
208 : extern Size BufferShmemSize(void);
209 : extern void BufferGetTag(Buffer buffer, RelFileNode *rnode,
210 : ForkNumber *forknum, BlockNumber *blknum);
211 :
212 : extern void MarkBufferDirtyHint(Buffer buffer, bool buffer_std);
213 :
214 : extern void UnlockBuffers(void);
215 : extern void LockBuffer(Buffer buffer, int mode);
216 : extern bool ConditionalLockBuffer(Buffer buffer);
217 : extern void LockBufferForCleanup(Buffer buffer);
218 : extern bool ConditionalLockBufferForCleanup(Buffer buffer);
219 : extern bool IsBufferCleanupOK(Buffer buffer);
220 : extern bool HoldingBufferPinThatDelaysRecovery(void);
221 :
222 : extern void AbortBufferIO(void);
223 :
224 : extern void BufmgrCommit(void);
225 : extern bool BgBufferSync(struct WritebackContext *wb_context);
226 :
227 : extern void AtProcExit_LocalBuffers(void);
228 :
229 : extern void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation);
230 :
231 : /* in freelist.c */
232 : extern BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype);
233 : extern void FreeAccessStrategy(BufferAccessStrategy strategy);
234 :
235 :
236 : /* inline functions */
237 :
238 : /*
239 : * Although this header file is nominally backend-only, certain frontend
240 : * programs like pg_waldump include it. For compilers that emit static
241 : * inline functions even when they're unused, that leads to unsatisfied
242 : * external references; hence hide these with #ifndef FRONTEND.
243 : */
244 :
245 : #ifndef FRONTEND
246 :
247 : /*
248 : * Check whether the given snapshot is too old to have safely read the given
249 : * page from the given table. If so, throw a "snapshot too old" error.
250 : *
251 : * This test generally needs to be performed after every BufferGetPage() call
252 : * that is executed as part of a scan. It is not needed for calls made for
253 : * modifying the page (for example, to position to the right place to insert a
254 : * new index tuple or for vacuuming). It may also be omitted where calls to
255 : * lower-level functions will have already performed the test.
256 : *
257 : * Note that a NULL snapshot argument is allowed and causes a fast return
258 : * without error; this is to support call sites which can be called from
259 : * either scans or index modification areas.
260 : *
261 : * For best performance, keep the tests that are fastest and/or most likely to
262 : * exclude a page from old snapshot testing near the front.
263 : */
264 : static inline void
265 4711457 : TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
266 : {
267 4711457 : Assert(relation != NULL);
268 :
269 4711457 : if (old_snapshot_threshold >= 0
270 0 : && (snapshot) != NULL
271 0 : && ((snapshot)->satisfies == HeapTupleSatisfiesMVCC
272 0 : || (snapshot)->satisfies == HeapTupleSatisfiesToast)
273 0 : && !XLogRecPtrIsInvalid((snapshot)->lsn)
274 0 : && PageGetLSN(page) > (snapshot)->lsn)
275 0 : TestForOldSnapshot_impl(snapshot, relation);
276 4711457 : }
277 :
278 : #endif /* FRONTEND */
279 :
280 : #endif /* BUFMGR_H */
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