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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) 1996-2021, 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 /*
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 */
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;
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;
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  */
175  ForkNumber forkNum,
176  BlockNumber blockNum);
178  BlockNumber blockNum);
179 extern bool ReadRecentBuffer(RelFileNode rnode, ForkNumber forkNum,
180  BlockNumber blockNum, Buffer recent_buffer);
181 extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
182 extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum,
183  BlockNumber blockNum, ReadBufferMode mode,
184  BufferAccessStrategy strategy);
186  ForkNumber forkNum, BlockNumber blockNum,
188 extern void ReleaseBuffer(Buffer buffer);
189 extern void UnlockReleaseBuffer(Buffer buffer);
190 extern void MarkBufferDirty(Buffer buffer);
191 extern void IncrBufferRefCount(Buffer buffer);
192 extern Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation,
193  BlockNumber blockNum);
194 
195 extern void InitBufferPool(void);
196 extern void InitBufferPoolAccess(void);
197 extern void AtEOXact_Buffers(bool isCommit);
198 extern void PrintBufferLeakWarning(Buffer buffer);
199 extern void CheckPointBuffers(int flags);
202  ForkNumber forkNum);
203 extern void FlushOneBuffer(Buffer buffer);
204 extern void FlushRelationBuffers(Relation rel);
205 extern void FlushRelationsAllBuffers(struct SMgrRelationData **smgrs, int nrels);
206 extern void FlushDatabaseBuffers(Oid dbid);
207 extern void DropRelFileNodeBuffers(struct SMgrRelationData *smgr_reln, ForkNumber *forkNum,
208  int nforks, BlockNumber *firstDelBlock);
209 extern void DropRelFileNodesAllBuffers(struct SMgrRelationData **smgr_reln, int nnodes);
210 extern void DropDatabaseBuffers(Oid dbid);
211 
212 #define RelationGetNumberOfBlocks(reln) \
213  RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM)
214 
215 extern bool BufferIsPermanent(Buffer buffer);
216 extern XLogRecPtr BufferGetLSNAtomic(Buffer buffer);
217 
218 #ifdef NOT_USED
219 extern void PrintPinnedBufs(void);
220 #endif
221 extern Size BufferShmemSize(void);
222 extern void BufferGetTag(Buffer buffer, RelFileNode *rnode,
223  ForkNumber *forknum, BlockNumber *blknum);
224 
225 extern void MarkBufferDirtyHint(Buffer buffer, bool buffer_std);
226 
227 extern void UnlockBuffers(void);
228 extern void LockBuffer(Buffer buffer, int mode);
229 extern bool ConditionalLockBuffer(Buffer buffer);
230 extern void LockBufferForCleanup(Buffer buffer);
231 extern bool ConditionalLockBufferForCleanup(Buffer buffer);
232 extern bool IsBufferCleanupOK(Buffer buffer);
233 extern bool HoldingBufferPinThatDelaysRecovery(void);
234 
235 extern void AbortBufferIO(void);
236 
237 extern void BufmgrCommit(void);
238 extern bool BgBufferSync(struct WritebackContext *wb_context);
239 
240 extern void AtProcExit_LocalBuffers(void);
241 
242 extern void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation);
243 
244 /* in freelist.c */
246 extern void FreeAccessStrategy(BufferAccessStrategy strategy);
247 
248 
249 /* inline functions */
250 
251 /*
252  * Although this header file is nominally backend-only, certain frontend
253  * programs like pg_waldump include it. For compilers that emit static
254  * inline functions even when they're unused, that leads to unsatisfied
255  * external references; hence hide these with #ifndef FRONTEND.
256  */
257 
258 #ifndef FRONTEND
259 
260 /*
261  * Check whether the given snapshot is too old to have safely read the given
262  * page from the given table. If so, throw a "snapshot too old" error.
263  *
264  * This test generally needs to be performed after every BufferGetPage() call
265  * that is executed as part of a scan. It is not needed for calls made for
266  * modifying the page (for example, to position to the right place to insert a
267  * new index tuple or for vacuuming). It may also be omitted where calls to
268  * lower-level functions will have already performed the test.
269  *
270  * Note that a NULL snapshot argument is allowed and causes a fast return
271  * without error; this is to support call sites which can be called from
272  * either scans or index modification areas.
273  *
274  * For best performance, keep the tests that are fastest and/or most likely to
275  * exclude a page from old snapshot testing near the front.
276  */
277 static inline void
278 TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
279 {
280  Assert(relation != NULL);
281 
282  if (old_snapshot_threshold >= 0
283  && (snapshot) != NULL
284  && ((snapshot)->snapshot_type == SNAPSHOT_MVCC
285  || (snapshot)->snapshot_type == SNAPSHOT_TOAST)
286  && !XLogRecPtrIsInvalid((snapshot)->lsn)
287  && PageGetLSN(page) > (snapshot)->lsn)
288  TestForOldSnapshot_impl(snapshot, relation);
289 }
290 
291 #endif /* FRONTEND */
292 
293 #endif /* BUFMGR_H */
void IncrBufferRefCount(Buffer buffer)
Definition: bufmgr.c:3806
static PgChecksumMode mode
Definition: pg_checksums.c:65
void PrintBufferLeakWarning(Buffer buffer)
Definition: bufmgr.c:2681
static void TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
Definition: bufmgr.h:278
void FlushDatabaseBuffers(Oid dbid)
Definition: bufmgr.c:3705
BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype)
Definition: freelist.c:542
PrefetchBufferResult PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
Definition: bufmgr.c:587
void AtEOXact_Buffers(bool isCommit)
Definition: bufmgr.c:2579
bool HoldingBufferPinThatDelaysRecovery(void)
Definition: bufmgr.c:4215
bool IsBufferCleanupOK(Buffer buffer)
Definition: bufmgr.c:4297
void FlushRelationBuffers(Relation rel)
Definition: bufmgr.c:3512
PrefetchBufferResult PrefetchSharedBuffer(struct SMgrRelationData *smgr_reln, ForkNumber forkNum, BlockNumber blockNum)
void UnlockReleaseBuffer(Buffer buffer)
Definition: bufmgr.c:3791
PGDLLIMPORT char * BufferBlocks
Definition: buf_init.c:21
int checkpoint_flush_after
Definition: bufmgr.c:156
void BufmgrCommit(void)
Definition: bufmgr.c:2734
PGDLLIMPORT int32 * LocalRefCount
Definition: localbuf.c:45
bool track_io_timing
Definition: bufmgr.c:135
void MarkBufferDirty(Buffer buffer)
Definition: bufmgr.c:1565
Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum, ReadBufferMode mode, BufferAccessStrategy strategy)
Definition: bufmgr.c:741
Size BufferShmemSize(void)
Definition: buf_init.c:156
BlockNumber BufferGetBlockNumber(Buffer buffer)
Definition: bufmgr.c:2748
uint32 BlockNumber
Definition: block.h:31
int effective_io_concurrency
Definition: bufmgr.c:143
void InitBufferPool(void)
Definition: buf_init.c:67
bool ConditionalLockBufferForCleanup(Buffer buffer)
Definition: bufmgr.c:4241
unsigned int Oid
Definition: postgres_ext.h:31
int bgwriter_lru_maxpages
Definition: bufmgr.c:133
Buffer recent_buffer
Definition: bufmgr.h:54
#define PGDLLIMPORT
Definition: c.h:1317
signed int int32
Definition: c.h:429
struct PrefetchBufferResult PrefetchBufferResult
PGDLLIMPORT int NLocBuffer
Definition: localbuf.c:41
double bgwriter_lru_multiplier
Definition: bufmgr.c:134
bool BgBufferSync(struct WritebackContext *wb_context)
Definition: bufmgr.c:2209
Buffer ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum, BlockNumber blockNum, ReadBufferMode mode, BufferAccessStrategy strategy)
Definition: bufmgr.c:780
void FlushRelationsAllBuffers(struct SMgrRelationData **smgrs, int nrels)
void AtProcExit_LocalBuffers(void)
Definition: localbuf.c:588
void UnlockBuffers(void)
Definition: bufmgr.c:3979
void LockBuffer(Buffer buffer, int mode)
Definition: bufmgr.c:4007
XLogRecPtr BufferGetLSNAtomic(Buffer buffer)
Definition: bufmgr.c:3008
void InitBufferPoolAccess(void)
Definition: bufmgr.c:2596
Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation, BlockNumber blockNum)
Definition: bufmgr.c:1628
void AbortBufferIO(void)
Definition: bufmgr.c:4477
bool ReadRecentBuffer(RelFileNode rnode, ForkNumber forkNum, BlockNumber blockNum, Buffer recent_buffer)
Definition: bufmgr.c:618
int bgwriter_flush_after
Definition: bufmgr.c:157
ForkNumber
Definition: relpath.h:40
void DropRelFileNodesAllBuffers(struct SMgrRelationData **smgr_reln, int nnodes)
bool zero_damaged_pages
Definition: bufmgr.c:132
#define XLogRecPtrIsInvalid(r)
Definition: xlogdefs.h:29
ReadBufferMode
Definition: bufmgr.h:37
void DropRelFileNodeBuffers(struct SMgrRelationData *smgr_reln, ForkNumber *forkNum, int nforks, BlockNumber *firstDelBlock)
void FlushOneBuffer(Buffer buffer)
Definition: bufmgr.c:3748
bool BufferIsPermanent(Buffer buffer)
Definition: bufmgr.c:2978
bool ConditionalLockBuffer(Buffer buffer)
Definition: bufmgr.c:4033
void BufferGetTag(Buffer buffer, RelFileNode *rnode, ForkNumber *forknum, BlockNumber *blknum)
Definition: bufmgr.c:2769
uint64 XLogRecPtr
Definition: xlogdefs.h:21
#define Assert(condition)
Definition: c.h:804
int backend_flush_after
Definition: bufmgr.c:158
BufferAccessStrategyType
Definition: bufmgr.h:27
BlockNumber RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
Definition: bufmgr.c:2935
size_t Size
Definition: c.h:540
void DropDatabaseBuffers(Oid dbid)
Definition: bufmgr.c:3408
#define PageGetLSN(page)
Definition: bufpage.h:366
PGDLLIMPORT int NBuffers
Definition: globals.c:135
void CheckPointBuffers(int flags)
Definition: bufmgr.c:2724
void ReleaseBuffer(Buffer buffer)
Definition: bufmgr.c:3768
int maintenance_io_concurrency
Definition: bufmgr.c:150
int old_snapshot_threshold
Definition: snapmgr.c:78
Buffer ReadBuffer(Relation reln, BlockNumber blockNum)
Definition: bufmgr.c:694
void MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
Definition: bufmgr.c:3838
void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation)
Definition: bufmgr.c:4848
void LockBufferForCleanup(Buffer buffer)
Definition: bufmgr.c:4064
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