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Rewrite the sinval messaging mechanism to reduce contention and avoid

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unnecessary cache resets.  The major changes are:

* When the queue overflows, we only issue a cache reset to the specific
backend or backends that still haven't read the oldest message, rather
than resetting everyone as in the original coding.

* When we observe backend(s) falling well behind, we signal SIGUSR1
to only one backend, the one that is furthest behind and doesn't already
have a signal outstanding for it.  When it finishes catching up, it will
in turn signal SIGUSR1 to the next-furthest-back guy, if there is one that
is far enough behind to justify a signal.  The PMSIGNAL_WAKEN_CHILDREN
mechanism is removed.

* We don't attempt to clean out dead messages after every message-receipt
operation; rather, we do it on the insertion side, and only when the queue
fullness passes certain thresholds.

* Split SInvalLock into SInvalReadLock and SInvalWriteLock so that readers
don't block writers nor vice versa (except during the infrequent queue
cleanout operations).

* Transfer multiple sinval messages for each acquisition of a read or
write lock.
This commit is contained in:
Tom Lane
2008-06-19 21:32:56 +00:00
parent 30dc388a0d
commit fad153ec45
8 changed files with 416 additions and 247 deletions
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43
src/backend/utils/cache/inval.c vendored
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@ -80,7 +80,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/cache/inval.c,v 1.85 2008/06/19 00:46:05 alvherre Exp $
* $PostgreSQL: pgsql/src/backend/utils/cache/inval.c,v 1.86 2008/06/19 21:32:56 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -203,7 +203,7 @@ AddInvalidationMessage(InvalidationChunk **listHdr,
if (chunk == NULL)
{
/* First time through; create initial chunk */
#define FIRSTCHUNKSIZE 16
#define FIRSTCHUNKSIZE 32
chunk = (InvalidationChunk *)
MemoryContextAlloc(CurTransactionContext,
sizeof(InvalidationChunk) +
@ -275,6 +275,23 @@ AppendInvalidationMessageList(InvalidationChunk **destHdr,
} \
} while (0)
/*
* Process a list of invalidation messages group-wise.
*
* As above, but the code fragment can handle an array of messages.
* The fragment should refer to the messages as msgs[], with n entries.
*/
#define ProcessMessageListMulti(listHdr, codeFragment) \
do { \
InvalidationChunk *_chunk; \
for (_chunk = (listHdr); _chunk != NULL; _chunk = _chunk->next) \
{ \
SharedInvalidationMessage *msgs = _chunk->msgs; \
int n = _chunk->nitems; \
codeFragment; \
} \
} while (0)
/* ----------------------------------------------------------------
* Invalidation set support functions
@ -371,6 +388,18 @@ ProcessInvalidationMessages(InvalidationListHeader *hdr,
ProcessMessageList(hdr->rclist, func(msg));
}
/*
* As above, but the function is able to process an array of messages
* rather than just one at a time.
*/
static void
ProcessInvalidationMessagesMulti(InvalidationListHeader *hdr,
void (*func) (const SharedInvalidationMessage *msgs, int n))
{
ProcessMessageListMulti(hdr->cclist, func(msgs, n));
ProcessMessageListMulti(hdr->rclist, func(msgs, n));
}
/* ----------------------------------------------------------------
* private support functions
* ----------------------------------------------------------------
@ -792,7 +821,7 @@ inval_twophase_postcommit(TransactionId xid, uint16 info,
case TWOPHASE_INFO_MSG:
msg = (SharedInvalidationMessage *) recdata;
Assert(len == sizeof(SharedInvalidationMessage));
SendSharedInvalidMessage(msg);
SendSharedInvalidMessages(msg, 1);
break;
case TWOPHASE_INFO_FILE_BEFORE:
RelationCacheInitFileInvalidate(true);
@ -850,8 +879,8 @@ AtEOXact_Inval(bool isCommit)
AppendInvalidationMessages(&transInvalInfo->PriorCmdInvalidMsgs,
&transInvalInfo->CurrentCmdInvalidMsgs);
ProcessInvalidationMessages(&transInvalInfo->PriorCmdInvalidMsgs,
SendSharedInvalidMessage);
ProcessInvalidationMessagesMulti(&transInvalInfo->PriorCmdInvalidMsgs,
SendSharedInvalidMessages);
if (transInvalInfo->RelcacheInitFileInval)
RelationCacheInitFileInvalidate(false);
@ -1033,8 +1062,8 @@ EndNonTransactionalInvalidation(void)
/* Send out the invals */
ProcessInvalidationMessages(&transInvalInfo->CurrentCmdInvalidMsgs,
LocalExecuteInvalidationMessage);
ProcessInvalidationMessages(&transInvalInfo->CurrentCmdInvalidMsgs,
SendSharedInvalidMessage);
ProcessInvalidationMessagesMulti(&transInvalInfo->CurrentCmdInvalidMsgs,
SendSharedInvalidMessages);
/* Clean up and release memory */
for (chunk = transInvalInfo->CurrentCmdInvalidMsgs.cclist;