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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.
This commit is contained in:
Tom Lane
2004-10-16 18:57:26 +00:00
parent 1c2de47746
commit fdd13f1568
6 changed files with 95 additions and 72 deletions
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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)
/*
* 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)
{
/*
* 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 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)
{