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Make large sequential scans and VACUUMs work in a limited-size "ring" of
buffers, rather than blowing out the whole shared-buffer arena. Aside from avoiding cache spoliation, this fixes the problem that VACUUM formerly tended to cause a WAL flush for every page it modified, because we had it hacked to use only a single buffer. Those flushes will now occur only once per ring-ful. The exact ring size, and the threshold for seqscans to switch into the ring usage pattern, remain under debate; but the infrastructure seems done. The key bit of infrastructure is a new optional BufferAccessStrategy object that can be passed to ReadBuffer operations; this replaces the former StrategyHintVacuum API. This patch also changes the buffer usage-count methodology a bit: we now advance usage_count when first pinning a buffer, rather than when last unpinning it. To preserve the behavior that a buffer's lifetime starts to decrease when it's released, the clock sweep code is modified to not decrement usage_count of pinned buffers. Work not done in this commit: teach GiST and GIN indexes to use the vacuum BufferAccessStrategy for vacuum-driven fetches. Original patch by Simon, reworked by Heikki and again by Tom.
This commit is contained in:
Tom Lane
@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.107 2007/04/30 03:23:48 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.108 2007/05/30 20:11:56 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -63,10 +63,13 @@ typedef struct AnlIndexData
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/* Default statistics target (GUC parameter) */
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int default_statistics_target = 10;
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/* A few variables that don't seem worth passing around as parameters */
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static int elevel = -1;
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static MemoryContext anl_context = NULL;
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static BufferAccessStrategy vac_strategy;
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static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
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int samplesize);
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@ -94,7 +97,8 @@ static bool std_typanalyze(VacAttrStats *stats);
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* analyze_rel() -- analyze one relation
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*/
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void
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analyze_rel(Oid relid, VacuumStmt *vacstmt)
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analyze_rel(Oid relid, VacuumStmt *vacstmt,
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BufferAccessStrategy bstrategy)
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{
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Relation onerel;
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int attr_cnt,
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@ -120,6 +124,8 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt)
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else
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elevel = DEBUG2;
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vac_strategy = bstrategy;
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/*
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* Use the current context for storing analysis info. vacuum.c ensures
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* that this context will be cleared when I return, thus releasing the
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@ -845,7 +851,7 @@ acquire_sample_rows(Relation onerel, HeapTuple *rows, int targrows,
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* looking at it. We don't maintain a lock on the page, so tuples
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* could get added to it, but we ignore such tuples.
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*/
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targbuffer = ReadBuffer(onerel, targblock);
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targbuffer = ReadBufferWithStrategy(onerel, targblock, vac_strategy);
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LockBuffer(targbuffer, BUFFER_LOCK_SHARE);
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targpage = BufferGetPage(targbuffer);
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maxoffset = PageGetMaxOffsetNumber(targpage);
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@ -13,7 +13,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.351 2007/05/17 15:28:29 alvherre Exp $
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* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.352 2007/05/30 20:11:57 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -191,6 +191,7 @@ ExecContext_Finish(ExecContext ec)
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*----------------------------------------------------------------------
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*/
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/* A few variables that don't seem worth passing around as parameters */
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static MemoryContext vac_context = NULL;
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static int elevel = -1;
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@ -198,6 +199,8 @@ static int elevel = -1;
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static TransactionId OldestXmin;
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static TransactionId FreezeLimit;
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static BufferAccessStrategy vac_strategy;
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/* non-export function prototypes */
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static List *get_rel_oids(List *relids, const RangeVar *vacrel,
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@ -257,14 +260,18 @@ static Size PageGetFreeSpaceWithFillFactor(Relation relation, Page page);
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* relation OIDs to be processed, and vacstmt->relation is ignored.
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* (The non-NIL case is currently only used by autovacuum.)
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*
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* bstrategy is normally given as NULL, but in autovacuum it can be passed
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* in to use the same buffer strategy object across multiple vacuum() calls.
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*
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* isTopLevel should be passed down from ProcessUtility.
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*
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* It is the caller's responsibility that both vacstmt and relids
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* It is the caller's responsibility that vacstmt, relids, and bstrategy
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* (if given) be allocated in a memory context that won't disappear
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* at transaction commit.
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*/
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void
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vacuum(VacuumStmt *vacstmt, List *relids, bool isTopLevel)
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vacuum(VacuumStmt *vacstmt, List *relids,
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BufferAccessStrategy bstrategy, bool isTopLevel)
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{
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const char *stmttype = vacstmt->vacuum ? "VACUUM" : "ANALYZE";
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volatile MemoryContext anl_context = NULL;
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@ -319,6 +326,19 @@ vacuum(VacuumStmt *vacstmt, List *relids, bool isTopLevel)
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ALLOCSET_DEFAULT_INITSIZE,
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ALLOCSET_DEFAULT_MAXSIZE);
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/*
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* If caller didn't give us a buffer strategy object, make one in the
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* cross-transaction memory context.
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*/
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if (bstrategy == NULL)
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{
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MemoryContext old_context = MemoryContextSwitchTo(vac_context);
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bstrategy = GetAccessStrategy(BAS_VACUUM);
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MemoryContextSwitchTo(old_context);
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}
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vac_strategy = bstrategy;
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/* Remember whether we are processing everything in the DB */
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all_rels = (relids == NIL && vacstmt->relation == NULL);
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@ -417,15 +437,7 @@ vacuum(VacuumStmt *vacstmt, List *relids, bool isTopLevel)
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else
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old_context = MemoryContextSwitchTo(anl_context);
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/*
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* Tell the buffer replacement strategy that vacuum is causing
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* the IO
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*/
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StrategyHintVacuum(true);
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analyze_rel(relid, vacstmt);
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StrategyHintVacuum(false);
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analyze_rel(relid, vacstmt, vac_strategy);
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if (use_own_xacts)
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CommitTransactionCommand();
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@ -441,8 +453,6 @@ vacuum(VacuumStmt *vacstmt, List *relids, bool isTopLevel)
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{
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/* Make sure cost accounting is turned off after error */
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VacuumCostActive = false;
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/* And reset buffer replacement strategy, too */
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StrategyHintVacuum(false);
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PG_RE_THROW();
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}
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PG_END_TRY();
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@ -1084,21 +1094,13 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
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*/
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toast_relid = onerel->rd_rel->reltoastrelid;
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/*
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* Tell the cache replacement strategy that vacuum is causing all
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* following IO
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*/
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StrategyHintVacuum(true);
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/*
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* Do the actual work --- either FULL or "lazy" vacuum
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*/
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if (vacstmt->full)
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full_vacuum_rel(onerel, vacstmt);
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else
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lazy_vacuum_rel(onerel, vacstmt);
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StrategyHintVacuum(false);
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lazy_vacuum_rel(onerel, vacstmt, vac_strategy);
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/* all done with this class, but hold lock until commit */
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relation_close(onerel, NoLock);
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@ -1290,7 +1292,7 @@ scan_heap(VRelStats *vacrelstats, Relation onerel,
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vacuum_delay_point();
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buf = ReadBuffer(onerel, blkno);
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buf = ReadBufferWithStrategy(onerel, blkno, vac_strategy);
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page = BufferGetPage(buf);
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/*
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@ -1730,7 +1732,7 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
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/*
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* Process this page of relation.
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*/
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buf = ReadBuffer(onerel, blkno);
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buf = ReadBufferWithStrategy(onerel, blkno, vac_strategy);
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page = BufferGetPage(buf);
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vacpage->offsets_free = 0;
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@ -1954,8 +1956,9 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
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nextTid = tp.t_data->t_ctid;
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priorXmax = HeapTupleHeaderGetXmax(tp.t_data);
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/* assume block# is OK (see heap_fetch comments) */
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nextBuf = ReadBuffer(onerel,
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ItemPointerGetBlockNumber(&nextTid));
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nextBuf = ReadBufferWithStrategy(onerel,
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ItemPointerGetBlockNumber(&nextTid),
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vac_strategy);
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nextPage = BufferGetPage(nextBuf);
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/* If bogus or unused slot, assume tp is end of chain */
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nextOffnum = ItemPointerGetOffsetNumber(&nextTid);
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@ -2091,8 +2094,9 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
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break; /* out of check-all-items loop */
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}
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tp.t_self = vtlp->this_tid;
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Pbuf = ReadBuffer(onerel,
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ItemPointerGetBlockNumber(&(tp.t_self)));
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Pbuf = ReadBufferWithStrategy(onerel,
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ItemPointerGetBlockNumber(&(tp.t_self)),
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vac_strategy);
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Ppage = BufferGetPage(Pbuf);
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Pitemid = PageGetItemId(Ppage,
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ItemPointerGetOffsetNumber(&(tp.t_self)));
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@ -2174,11 +2178,14 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
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/* Get page to move from */
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tuple.t_self = vtmove[ti].tid;
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Cbuf = ReadBuffer(onerel,
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ItemPointerGetBlockNumber(&(tuple.t_self)));
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Cbuf = ReadBufferWithStrategy(onerel,
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ItemPointerGetBlockNumber(&(tuple.t_self)),
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vac_strategy);
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/* Get page to move to */
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dst_buffer = ReadBuffer(onerel, destvacpage->blkno);
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dst_buffer = ReadBufferWithStrategy(onerel,
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destvacpage->blkno,
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vac_strategy);
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LockBuffer(dst_buffer, BUFFER_LOCK_EXCLUSIVE);
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if (dst_buffer != Cbuf)
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@ -2239,7 +2246,9 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
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if (i == num_fraged_pages)
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break; /* can't move item anywhere */
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dst_vacpage = fraged_pages->pagedesc[i];
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dst_buffer = ReadBuffer(onerel, dst_vacpage->blkno);
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dst_buffer = ReadBufferWithStrategy(onerel,
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dst_vacpage->blkno,
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vac_strategy);
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LockBuffer(dst_buffer, BUFFER_LOCK_EXCLUSIVE);
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dst_page = BufferGetPage(dst_buffer);
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/* if this page was not used before - clean it */
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@ -2386,7 +2395,9 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
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Page page;
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/* this page was not used as a move target, so must clean it */
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buf = ReadBuffer(onerel, (*curpage)->blkno);
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buf = ReadBufferWithStrategy(onerel,
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(*curpage)->blkno,
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vac_strategy);
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LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
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page = BufferGetPage(buf);
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if (!PageIsEmpty(page))
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@ -2470,7 +2481,7 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
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int uncnt;
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int num_tuples = 0;
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buf = ReadBuffer(onerel, vacpage->blkno);
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buf = ReadBufferWithStrategy(onerel, vacpage->blkno, vac_strategy);
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LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
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page = BufferGetPage(buf);
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maxoff = PageGetMaxOffsetNumber(page);
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@ -2859,7 +2870,7 @@ update_hint_bits(Relation rel, VacPageList fraged_pages, int num_fraged_pages,
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break; /* no need to scan any further */
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if ((*curpage)->offsets_used == 0)
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continue; /* this page was never used as a move dest */
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buf = ReadBuffer(rel, (*curpage)->blkno);
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buf = ReadBufferWithStrategy(rel, (*curpage)->blkno, vac_strategy);
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LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
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page = BufferGetPage(buf);
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max_offset = PageGetMaxOffsetNumber(page);
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@ -2925,7 +2936,9 @@ vacuum_heap(VRelStats *vacrelstats, Relation onerel, VacPageList vacuum_pages)
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if ((*vacpage)->offsets_free > 0)
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{
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buf = ReadBuffer(onerel, (*vacpage)->blkno);
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buf = ReadBufferWithStrategy(onerel,
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(*vacpage)->blkno,
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vac_strategy);
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LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
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vacuum_page(onerel, buf, *vacpage);
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UnlockReleaseBuffer(buf);
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@ -3012,6 +3025,7 @@ scan_index(Relation indrel, double num_tuples)
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ivinfo.vacuum_full = true;
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ivinfo.message_level = elevel;
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ivinfo.num_heap_tuples = num_tuples;
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ivinfo.strategy = vac_strategy;
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stats = index_vacuum_cleanup(&ivinfo, NULL);
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@ -3077,6 +3091,7 @@ vacuum_index(VacPageList vacpagelist, Relation indrel,
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ivinfo.vacuum_full = true;
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ivinfo.message_level = elevel;
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ivinfo.num_heap_tuples = num_tuples + keep_tuples;
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ivinfo.strategy = vac_strategy;
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/* Do bulk deletion */
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stats = index_bulk_delete(&ivinfo, NULL, tid_reaped, (void *) vacpagelist);
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@ -36,7 +36,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.89 2007/05/17 15:28:29 alvherre Exp $
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* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.90 2007/05/30 20:11:57 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -96,11 +96,14 @@ typedef struct LVRelStats
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} LVRelStats;
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/* A few variables that don't seem worth passing around as parameters */
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static int elevel = -1;
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static TransactionId OldestXmin;
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static TransactionId FreezeLimit;
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static BufferAccessStrategy vac_strategy;
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/* non-export function prototypes */
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static void lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
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@ -138,7 +141,8 @@ static int vac_cmp_page_spaces(const void *left, const void *right);
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* and locked the relation.
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*/
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void
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lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
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lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
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BufferAccessStrategy bstrategy)
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{
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LVRelStats *vacrelstats;
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Relation *Irel;
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@ -158,6 +162,8 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
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else
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elevel = DEBUG2;
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vac_strategy = bstrategy;
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vacuum_set_xid_limits(vacstmt->freeze_min_age, onerel->rd_rel->relisshared,
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&OldestXmin, &FreezeLimit);
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@ -318,7 +324,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
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vacrelstats->num_index_scans++;
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}
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buf = ReadBuffer(onerel, blkno);
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buf = ReadBufferWithStrategy(onerel, blkno, vac_strategy);
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/* Initially, we only need shared access to the buffer */
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LockBuffer(buf, BUFFER_LOCK_SHARE);
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@ -586,7 +592,7 @@ lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
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vacuum_delay_point();
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tblk = ItemPointerGetBlockNumber(&vacrelstats->dead_tuples[tupindex]);
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buf = ReadBuffer(onerel, tblk);
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buf = ReadBufferWithStrategy(onerel, tblk, vac_strategy);
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LockBufferForCleanup(buf);
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tupindex = lazy_vacuum_page(onerel, tblk, buf, tupindex, vacrelstats);
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/* Now that we've compacted the page, record its available space */
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@ -684,6 +690,7 @@ lazy_vacuum_index(Relation indrel,
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ivinfo.message_level = elevel;
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/* We don't yet know rel_tuples, so pass -1 */
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ivinfo.num_heap_tuples = -1;
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ivinfo.strategy = vac_strategy;
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/* Do bulk deletion */
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*stats = index_bulk_delete(&ivinfo, *stats,
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@ -713,6 +720,7 @@ lazy_cleanup_index(Relation indrel,
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ivinfo.vacuum_full = false;
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ivinfo.message_level = elevel;
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ivinfo.num_heap_tuples = vacrelstats->rel_tuples;
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ivinfo.strategy = vac_strategy;
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stats = index_vacuum_cleanup(&ivinfo, stats);
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@ -869,7 +877,7 @@ count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats)
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blkno--;
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buf = ReadBuffer(onerel, blkno);
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buf = ReadBufferWithStrategy(onerel, blkno, vac_strategy);
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/* In this phase we only need shared access to the buffer */
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LockBuffer(buf, BUFFER_LOCK_SHARE);
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