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bufmgr.h
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1 /*-------------------------------------------------------------------------
2  *
3  * bufmgr.h
4  * POSTGRES buffer manager definitions.
5  *
6  *
7  * Portions Copyright (c) 1996-2019, 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() */
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 */
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 */
48 
49 /* forward declared, to avoid having to expose buf_internals.h here */
50 struct WritebackContext;
51 
52 /* in globals.c ... this duplicates miscadmin.h */
53 extern PGDLLIMPORT int NBuffers;
54 
55 /* in bufmgr.c */
56 extern bool zero_damaged_pages;
57 extern int bgwriter_lru_maxpages;
58 extern double bgwriter_lru_multiplier;
59 extern bool track_io_timing;
60 extern int target_prefetch_pages;
61 
62 extern int checkpoint_flush_after;
63 extern int backend_flush_after;
64 extern int bgwriter_flush_after;
65 
66 /* in buf_init.c */
67 extern PGDLLIMPORT char *BufferBlocks;
68 
69 /* in guc.c */
70 extern int effective_io_concurrency;
71 
72 /* in localbuf.c */
73 extern PGDLLIMPORT int NLocBuffer;
76 
77 /* upper limit for effective_io_concurrency */
78 #define MAX_IO_CONCURRENCY 1000
79 
80 /* special block number for ReadBuffer() */
81 #define P_NEW InvalidBlockNumber /* grow the file to get a new page */
82 
83 /*
84  * Buffer content lock modes (mode argument for LockBuffer())
85  */
86 #define BUFFER_LOCK_UNLOCK 0
87 #define BUFFER_LOCK_SHARE 1
88 #define BUFFER_LOCK_EXCLUSIVE 2
89 
90 /*
91  * These routines are beaten on quite heavily, hence the macroization.
92  */
93 
94 /*
95  * BufferIsValid
96  * True iff the given buffer number is valid (either as a shared
97  * or local buffer).
98  *
99  * Note: For a long time this was defined the same as BufferIsPinned,
100  * that is it would say False if you didn't hold a pin on the buffer.
101  * I believe this was bogus and served only to mask logic errors.
102  * Code should always know whether it has a buffer reference,
103  * independently of the pin state.
104  *
105  * Note: For a further long time this was not quite the inverse of the
106  * BufferIsInvalid() macro, in that it also did sanity checks to verify
107  * that the buffer number was in range. Most likely, this macro was
108  * originally intended only to be used in assertions, but its use has
109  * since expanded quite a bit, and the overhead of making those checks
110  * even in non-assert-enabled builds can be significant. Thus, we've
111  * now demoted the range checks to assertions within the macro itself.
112  */
113 #define BufferIsValid(bufnum) \
114 ( \
115  AssertMacro((bufnum) <= NBuffers && (bufnum) >= -NLocBuffer), \
116  (bufnum) != InvalidBuffer \
117 )
118 
119 /*
120  * BufferGetBlock
121  * Returns a reference to a disk page image associated with a buffer.
122  *
123  * Note:
124  * Assumes buffer is valid.
125  */
126 #define BufferGetBlock(buffer) \
127 ( \
128  AssertMacro(BufferIsValid(buffer)), \
129  BufferIsLocal(buffer) ? \
130  LocalBufferBlockPointers[-(buffer) - 1] \
131  : \
132  (Block) (BufferBlocks + ((Size) ((buffer) - 1)) * BLCKSZ) \
133 )
134 
135 /*
136  * BufferGetPageSize
137  * Returns the page size within a buffer.
138  *
139  * Notes:
140  * Assumes buffer is valid.
141  *
142  * The buffer can be a raw disk block and need not contain a valid
143  * (formatted) disk page.
144  */
145 /* XXX should dig out of buffer descriptor */
146 #define BufferGetPageSize(buffer) \
147 ( \
148  AssertMacro(BufferIsValid(buffer)), \
149  (Size)BLCKSZ \
150 )
151 
152 /*
153  * BufferGetPage
154  * Returns the page associated with a buffer.
155  *
156  * When this is called as part of a scan, there may be a need for a nearby
157  * call to TestForOldSnapshot(). See the definition of that for details.
158  */
159 #define BufferGetPage(buffer) ((Page)BufferGetBlock(buffer))
160 
161 /*
162  * prototypes for functions in bufmgr.c
163  */
164 extern bool ComputeIoConcurrency(int io_concurrency, double *target);
165 extern void PrefetchBuffer(Relation reln, ForkNumber forkNum,
166  BlockNumber blockNum);
167 extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
168 extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum,
169  BlockNumber blockNum, ReadBufferMode mode,
170  BufferAccessStrategy strategy);
172  ForkNumber forkNum, BlockNumber blockNum,
174 extern void ReleaseBuffer(Buffer buffer);
175 extern void UnlockReleaseBuffer(Buffer buffer);
176 extern void MarkBufferDirty(Buffer buffer);
177 extern void IncrBufferRefCount(Buffer buffer);
178 extern Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation,
179  BlockNumber blockNum);
180 
181 extern void InitBufferPool(void);
182 extern void InitBufferPoolAccess(void);
183 extern void InitBufferPoolBackend(void);
184 extern void AtEOXact_Buffers(bool isCommit);
185 extern void PrintBufferLeakWarning(Buffer buffer);
186 extern void CheckPointBuffers(int flags);
189  ForkNumber forkNum);
190 extern void FlushOneBuffer(Buffer buffer);
191 extern void FlushRelationBuffers(Relation rel);
192 extern void FlushDatabaseBuffers(Oid dbid);
194  ForkNumber forkNum, BlockNumber firstDelBlock);
195 extern void DropRelFileNodesAllBuffers(RelFileNodeBackend *rnodes, int nnodes);
196 extern void DropDatabaseBuffers(Oid dbid);
197 
198 #define RelationGetNumberOfBlocks(reln) \
199  RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM)
200 
201 extern bool BufferIsPermanent(Buffer buffer);
202 extern XLogRecPtr BufferGetLSNAtomic(Buffer buffer);
203 
204 #ifdef NOT_USED
205 extern void PrintPinnedBufs(void);
206 #endif
207 extern Size BufferShmemSize(void);
208 extern void BufferGetTag(Buffer buffer, RelFileNode *rnode,
209  ForkNumber *forknum, BlockNumber *blknum);
210 
211 extern void MarkBufferDirtyHint(Buffer buffer, bool buffer_std);
212 
213 extern void UnlockBuffers(void);
214 extern void LockBuffer(Buffer buffer, int mode);
215 extern bool ConditionalLockBuffer(Buffer buffer);
216 extern void LockBufferForCleanup(Buffer buffer);
217 extern bool ConditionalLockBufferForCleanup(Buffer buffer);
218 extern bool IsBufferCleanupOK(Buffer buffer);
219 extern bool HoldingBufferPinThatDelaysRecovery(void);
220 
221 extern void AbortBufferIO(void);
222 
223 extern void BufmgrCommit(void);
224 extern bool BgBufferSync(struct WritebackContext *wb_context);
225 
226 extern void AtProcExit_LocalBuffers(void);
227 
228 extern void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation);
229 
230 /* in freelist.c */
232 extern void FreeAccessStrategy(BufferAccessStrategy strategy);
233 
234 
235 /* inline functions */
236 
237 /*
238  * Although this header file is nominally backend-only, certain frontend
239  * programs like pg_waldump include it. For compilers that emit static
240  * inline functions even when they're unused, that leads to unsatisfied
241  * external references; hence hide these with #ifndef FRONTEND.
242  */
243 
244 #ifndef FRONTEND
245 
246 /*
247  * Check whether the given snapshot is too old to have safely read the given
248  * page from the given table. If so, throw a "snapshot too old" error.
249  *
250  * This test generally needs to be performed after every BufferGetPage() call
251  * that is executed as part of a scan. It is not needed for calls made for
252  * modifying the page (for example, to position to the right place to insert a
253  * new index tuple or for vacuuming). It may also be omitted where calls to
254  * lower-level functions will have already performed the test.
255  *
256  * Note that a NULL snapshot argument is allowed and causes a fast return
257  * without error; this is to support call sites which can be called from
258  * either scans or index modification areas.
259  *
260  * For best performance, keep the tests that are fastest and/or most likely to
261  * exclude a page from old snapshot testing near the front.
262  */
263 static inline void
264 TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
265 {
266  Assert(relation != NULL);
267 
268  if (old_snapshot_threshold >= 0
269  && (snapshot) != NULL
270  && ((snapshot)->snapshot_type == SNAPSHOT_MVCC
271  || (snapshot)->snapshot_type == SNAPSHOT_TOAST)
272  && !XLogRecPtrIsInvalid((snapshot)->lsn)
273  && PageGetLSN(page) > (snapshot)->lsn)
274  TestForOldSnapshot_impl(snapshot, relation);
275 }
276 
277 #endif /* FRONTEND */
278 
279 #endif /* BUFMGR_H */
void IncrBufferRefCount(Buffer buffer)
Definition: bufmgr.c:3391
static PgChecksumMode mode
Definition: pg_checksums.c:61
void PrintBufferLeakWarning(Buffer buffer)
Definition: bufmgr.c:2539
static void TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
Definition: bufmgr.h:264
void FlushDatabaseBuffers(Oid dbid)
Definition: bufmgr.c:3290
BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype)
Definition: freelist.c:542
bool ComputeIoConcurrency(int io_concurrency, double *target)
Definition: bufmgr.c:469
void AtEOXact_Buffers(bool isCommit)
Definition: bufmgr.c:2423
bool HoldingBufferPinThatDelaysRecovery(void)
Definition: bufmgr.c:3736
bool IsBufferCleanupOK(Buffer buffer)
Definition: bufmgr.c:3818
void FlushRelationBuffers(Relation rel)
Definition: bufmgr.c:3192
void UnlockReleaseBuffer(Buffer buffer)
Definition: bufmgr.c:3376
PGDLLIMPORT char * BufferBlocks
Definition: buf_init.c:22
int checkpoint_flush_after
Definition: bufmgr.c:119
void BufmgrCommit(void)
Definition: bufmgr.c:2599
PGDLLIMPORT int32 * LocalRefCount
Definition: localbuf.c:45
bool track_io_timing
Definition: bufmgr.c:112
void MarkBufferDirty(Buffer buffer)
Definition: bufmgr.c:1458
Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum, ReadBufferMode mode, BufferAccessStrategy strategy)
Definition: bufmgr.c:642
Size BufferShmemSize(void)
Definition: buf_init.c:161
BlockNumber BufferGetBlockNumber(Buffer buffer)
Definition: bufmgr.c:2613
uint32 BlockNumber
Definition: block.h:31
int effective_io_concurrency
Definition: bufmgr.c:113
void InitBufferPool(void)
Definition: buf_init.c:68
bool ConditionalLockBufferForCleanup(Buffer buffer)
Definition: bufmgr.c:3762
unsigned int Oid
Definition: postgres_ext.h:31
int bgwriter_lru_maxpages
Definition: bufmgr.c:110
void InitBufferPoolBackend(void)
Definition: bufmgr.c:2469
#define PGDLLIMPORT
Definition: c.h:1229
signed int int32
Definition: c.h:346
PGDLLIMPORT int NLocBuffer
Definition: localbuf.c:41
void DropRelFileNodesAllBuffers(RelFileNodeBackend *rnodes, int nnodes)
Definition: bufmgr.c:2984
double bgwriter_lru_multiplier
Definition: bufmgr.c:111
bool BgBufferSync(struct WritebackContext *wb_context)
Definition: bufmgr.c:2053
Buffer ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum, BlockNumber blockNum, ReadBufferMode mode, BufferAccessStrategy strategy)
Definition: bufmgr.c:684
void AtProcExit_LocalBuffers(void)
Definition: localbuf.c:583
void UnlockBuffers(void)
Definition: bufmgr.c:3562
void LockBuffer(Buffer buffer, int mode)
Definition: bufmgr.c:3590
XLogRecPtr BufferGetLSNAtomic(Buffer buffer)
Definition: bufmgr.c:2876
void InitBufferPoolAccess(void)
Definition: bufmgr.c:2445
Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation, BlockNumber blockNum)
Definition: bufmgr.c:1521
void AbortBufferIO(void)
Definition: bufmgr.c:4018
int bgwriter_flush_after
Definition: bufmgr.c:120
ForkNumber
Definition: relpath.h:40
bool zero_damaged_pages
Definition: bufmgr.c:109
void DropRelFileNodeBuffers(RelFileNodeBackend rnode, ForkNumber forkNum, BlockNumber firstDelBlock)
Definition: bufmgr.c:2927
#define XLogRecPtrIsInvalid(r)
Definition: xlogdefs.h:29
ReadBufferMode
Definition: bufmgr.h:37
void PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
Definition: bufmgr.c:531
void FlushOneBuffer(Buffer buffer)
Definition: bufmgr.c:3333
bool BufferIsPermanent(Buffer buffer)
Definition: bufmgr.c:2846
bool ConditionalLockBuffer(Buffer buffer)
Definition: bufmgr.c:3616
void BufferGetTag(Buffer buffer, RelFileNode *rnode, ForkNumber *forknum, BlockNumber *blknum)
Definition: bufmgr.c:2634
uint64 XLogRecPtr
Definition: xlogdefs.h:21
#define Assert(condition)
Definition: c.h:732
int backend_flush_after
Definition: bufmgr.c:121
BufferAccessStrategyType
Definition: bufmgr.h:27
BlockNumber RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
Definition: bufmgr.c:2800
size_t Size
Definition: c.h:466
void DropDatabaseBuffers(Oid dbid)
Definition: bufmgr.c:3087
#define PageGetLSN(page)
Definition: bufpage.h:366
PGDLLIMPORT int NBuffers
Definition: globals.c:131
void CheckPointBuffers(int flags)
Definition: bufmgr.c:2582
void ReleaseBuffer(Buffer buffer)
Definition: bufmgr.c:3353
int old_snapshot_threshold
Definition: snapmgr.c:75
Buffer ReadBuffer(Relation reln, BlockNumber blockNum)
Definition: bufmgr.c:596
void MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
Definition: bufmgr.c:3423
void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation)
Definition: bufmgr.c:4396
void LockBufferForCleanup(Buffer buffer)
Definition: bufmgr.c:3647
int Buffer
Definition: buf.h:23
PGDLLIMPORT Block * LocalBufferBlockPointers
Definition: localbuf.c:44
void FreeAccessStrategy(BufferAccessStrategy strategy)
Definition: freelist.c:597
Pointer Page
Definition: bufpage.h:78
void * Block
Definition: bufmgr.h:24
int target_prefetch_pages
Definition: bufmgr.c:130