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Give the ResourceOwner mechanism full responsibility for releasing buffer

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pins at end of transaction, and reduce AtEOXact_Buffers to an Assert
cross-check that this was done correctly.  When not USE_ASSERT_CHECKING,
AtEOXact_Buffers is a complete no-op.  This gets rid of an O(NBuffers)
bottleneck during transaction commit/abort, which recent testing has shown
becomes significant above a few tens of thousands of shared buffers.
REL8_0_STABLE
Tom Lane 21 years ago
parent 1c2de47746
commit fdd13f1568
6 changed files with 95 additions and 72 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 6
      src/backend/access/transam/xact.c
  2. 75
      src/backend/storage/buffer/bufmgr.c
  3. 19
      src/backend/storage/buffer/localbuf.c
  4. 10
      src/backend/storage/lmgr/proc.c
  5. 53
      src/backend/utils/resowner/resowner.c
  6. 4
      src/include/storage/bufmgr.h

6
src/backend/access/transam/xact.c
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@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.191 2004/10/04 21:52:14 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.192 2004/10/16 18:57:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1528,6 +1528,9 @@ CommitTransaction(void)
RESOURCE_RELEASE_BEFORE_LOCKS,
true, true);
/* Check we've released all buffer pins */
AtEOXact_Buffers(true);
/*
* Make catalog changes visible to all backends. This has to happen
* after relcache references are dropped (see comments for
@ -1684,6 +1687,7 @@ AbortTransaction(void)
ResourceOwnerRelease(TopTransactionResourceOwner,
RESOURCE_RELEASE_BEFORE_LOCKS,
false, true);
AtEOXact_Buffers(false);
AtEOXact_Inval(false);
smgrDoPendingDeletes(false);
ResourceOwnerRelease(TopTransactionResourceOwner,

75
src/backend/storage/buffer/bufmgr.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.179 2004/10/16 18:05:06 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.180 2004/10/16 18:57:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -851,35 +851,45 @@ ResetBufferUsage(void)
/*
* AtEOXact_Buffers - clean up at end of transaction.
*
* During abort, we need to release any buffer pins we're holding
* (this cleans up in case ereport interrupted a routine that pins a
* buffer). During commit, we shouldn't need to do that, but check
* anyway to see if anyone leaked a buffer reference count.
* As of PostgreSQL 8.0, buffer pins should get released by the
* ResourceOwner mechanism. This routine is just a debugging
* cross-check that no pins remain.
*/
void
AtEOXact_Buffers(bool isCommit)
{
#ifdef USE_ASSERT_CHECKING
int i;
for (i = 0; i < NBuffers; i++)
{
Assert(PrivateRefCount[i] == 0);
}
AtEOXact_LocalBuffers(isCommit);
#endif
}
/*
* Ensure we have released all shared-buffer locks and pins during backend exit
*/
void
AtProcExit_Buffers(void)
{
int i;
AbortBufferIO();
UnlockBuffers();
for (i = 0; i < NBuffers; i++)
{
if (PrivateRefCount[i] != 0)
{
BufferDesc *buf = &(BufferDescriptors[i]);
if (isCommit)
elog(WARNING,
"buffer refcount leak: [%03d] "
"(rel=%u/%u/%u, blockNum=%u, flags=0x%x, refcount=%u %d)",
i,
buf->tag.rnode.spcNode, buf->tag.rnode.dbNode,
buf->tag.rnode.relNode,
buf->tag.blockNum, buf->flags,
buf->refcount, PrivateRefCount[i]);
/*
* We don't worry about updating the ResourceOwner structures;
* resowner.c will clear them for itself.
* We don't worry about updating ResourceOwner; if we even got
* here, it suggests that ResourceOwners are messed up.
*/
PrivateRefCount[i] = 1; /* make sure we release shared pin */
LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
@ -888,8 +898,37 @@ AtEOXact_Buffers(bool isCommit)
Assert(PrivateRefCount[i] == 0);
}
}
}
AtEOXact_LocalBuffers(isCommit);
/*
* Helper routine to issue warnings when a buffer is unexpectedly pinned
*/
void
PrintBufferLeakWarning(Buffer buffer)
{
BufferDesc *buf;
int32 loccount;
Assert(BufferIsValid(buffer));
if (BufferIsLocal(buffer))
{
buf = &LocalBufferDescriptors[-buffer - 1];
loccount = LocalRefCount[-buffer - 1];
}
else
{
buf = &BufferDescriptors[buffer - 1];
loccount = PrivateRefCount[buffer - 1];
}
elog(WARNING,
"buffer refcount leak: [%03d] "
"(rel=%u/%u/%u, blockNum=%u, flags=0x%x, refcount=%u %d)",
buffer,
buf->tag.rnode.spcNode, buf->tag.rnode.dbNode,
buf->tag.rnode.relNode,
buf->tag.blockNum, buf->flags,
buf->refcount, loccount);
}
/*

19
src/backend/storage/buffer/localbuf.c
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@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.59 2004/08/29 05:06:47 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.60 2004/10/16 18:57:24 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -232,23 +232,12 @@ InitLocalBuffer(void)
void
AtEOXact_LocalBuffers(bool isCommit)
{
#ifdef USE_ASSERT_CHECKING
int i;
for (i = 0; i < NLocBuffer; i++)
{
if (LocalRefCount[i] != 0)
{
BufferDesc *buf = &(LocalBufferDescriptors[i]);
if (isCommit)
elog(WARNING,
"local buffer leak: [%03d] (rel=%u/%u/%u, blockNum=%u, flags=0x%x, refcount=%u %d)",
i,
buf->tag.rnode.spcNode, buf->tag.rnode.dbNode,
buf->tag.rnode.relNode, buf->tag.blockNum, buf->flags,
buf->refcount, LocalRefCount[i]);
LocalRefCount[i] = 0;
}
Assert(LocalRefCount[i] == 0);
}
#endif
}

10
src/backend/storage/lmgr/proc.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.154 2004/09/29 15:15:55 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.155 2004/10/16 18:57:24 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -461,9 +461,7 @@ ProcKill(int code, Datum arg)
* shutdown callback registered by the bufmgr ... but we must do this
* *after* LWLockReleaseAll and *before* zapping MyProc.
*/
AbortBufferIO();
UnlockBuffers();
AtEOXact_Buffers(false);
AtProcExit_Buffers();
/* Get off any wait queue I might be on */
LockWaitCancel();
@ -509,9 +507,7 @@ DummyProcKill(int code, Datum arg)
LWLockReleaseAll();
/* Release buffer locks and pins, too */
AbortBufferIO();
UnlockBuffers();
AtEOXact_Buffers(false);
AtProcExit_Buffers();
/* I can't be on regular lock queues, so needn't check */

53
src/backend/utils/resowner/resowner.c
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@ -14,7 +14,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/resowner/resowner.c,v 1.7 2004/08/30 02:54:40 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/resowner/resowner.c,v 1.8 2004/10/16 18:57:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -191,37 +191,30 @@ ResourceOwnerReleaseInternal(ResourceOwner owner,
if (phase == RESOURCE_RELEASE_BEFORE_LOCKS)
{
/* Release buffer pins */
if (isTopLevel)
{
/*
* For a top-level xact we are going to release all buffers,
* so just do a single bufmgr call at the top of the
* recursion.
*/
if (owner == TopTransactionResourceOwner)
AtEOXact_Buffers(isCommit);
/* Mark object as owning no buffers, just for sanity */
owner->nbuffers = 0;
}
else
/*
* Release buffer pins. Note that ReleaseBuffer will
* remove the buffer entry from my list, so I just have to
* iterate till there are none.
*
* During a commit, there shouldn't be any remaining pins ---
* that would indicate failure to clean up the executor correctly ---
* so issue warnings. In the abort case, just clean up quietly.
*
* XXX this is fairly inefficient due to multiple BufMgrLock
* grabs if there are lots of buffers to be released, but we
* don't expect many (indeed none in the success case) so it's
* probably not worth optimizing.
*
* We are however careful to release back-to-front, so as to
* avoid O(N^2) behavior in ResourceOwnerForgetBuffer().
*/
while (owner->nbuffers > 0)
{
/*
* Release buffers retail. Note that ReleaseBuffer will
* remove the buffer entry from my list, so I just have to
* iterate till there are none.
*
* XXX this is fairly inefficient due to multiple BufMgrLock
* grabs if there are lots of buffers to be released, but we
* don't expect many (indeed none in the success case) so it's
* probably not worth optimizing.
*
* We are however careful to release back-to-front, so as to
* avoid O(N^2) behavior in ResourceOwnerForgetBuffer().
*/
while (owner->nbuffers > 0)
ReleaseBuffer(owner->buffers[owner->nbuffers - 1]);
if (isCommit)
PrintBufferLeakWarning(owner->buffers[owner->nbuffers - 1]);
ReleaseBuffer(owner->buffers[owner->nbuffers - 1]);
}
/* Release relcache references */
if (isTopLevel)
{

4
src/include/storage/bufmgr.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/storage/bufmgr.h,v 1.87 2004/10/15 22:40:25 tgl Exp $
* $PostgreSQL: pgsql/src/include/storage/bufmgr.h,v 1.88 2004/10/16 18:57:26 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -122,6 +122,8 @@ extern void InitBufferPoolAccess(void);
extern char *ShowBufferUsage(void);
extern void ResetBufferUsage(void);
extern void AtEOXact_Buffers(bool isCommit);
extern void AtProcExit_Buffers(void);
extern void PrintBufferLeakWarning(Buffer buffer);
extern void FlushBufferPool(void);
extern BlockNumber BufferGetBlockNumber(Buffer buffer);
extern BlockNumber RelationGetNumberOfBlocks(Relation relation);

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