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Handle impending sinval queue overflow by means of a separate signal

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(SIGUSR1, which we have not been using recently) instead of piggybacking
on SIGUSR2-driven NOTIFY processing.  This has several good results:
the processing needed to drain the sinval queue is a lot less than the
processing needed to answer a NOTIFY; there's less contention since we
don't have a bunch of backends all trying to acquire exclusive lock on
pg_listener; backends that are sitting inside a transaction block can
still drain the queue, whereas NOTIFY processing can't run if there's
an open transaction block.  (This last is a fairly serious issue that
I don't think we ever recognized before --- with clients like JDBC that
tend to sit with open transaction blocks, the sinval queue draining
mechanism never really worked as intended, probably resulting in a lot
of useless cache-reset overhead.)  This is the last of several proposed
changes in response to Philip Warner's recent report of sinval-induced
performance problems.
This commit is contained in:
Tom Lane
2004-05-23 03:50:45 +00:00
parent 4d86ae4260
commit ebfc56d3fb
8 changed files with 289 additions and 37 deletions
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8
src/backend/postmaster/postmaster.c
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@@ -37,7 +37,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.393 2004/05/21 05:07:57 tgl Exp $
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.394 2004/05/23 03:50:45 tgl Exp $
*
* NOTES
*
@@ -2861,11 +2861,11 @@ sigusr1_handler(SIGNAL_ARGS)
if (CheckPostmasterSignal(PMSIGNAL_WAKEN_CHILDREN))
{
/*
* Send SIGUSR2 to all children (triggers AsyncNotifyHandler). See
* storage/ipc/sinvaladt.c for the use of this.
* Send SIGUSR1 to all children (triggers CatchupInterruptHandler).
* See storage/ipc/sinval[adt].c for the use of this.
*/
if (Shutdown == NoShutdown)
SignalChildren(SIGUSR2);
SignalChildren(SIGUSR1);
}
PG_SETMASK(&UnBlockSig);