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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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15
src/backend/tcop/postgres.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.413 2004/05/21 05:07:58 tgl Exp $
* $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.414 2004/05/23 03:50:45 tgl Exp $
*
* NOTES
* this is the "main" module of the postgres backend and
@ -52,6 +52,7 @@
#include "storage/ipc.h"
#include "storage/pg_shmem.h"
#include "storage/proc.h"
#include "storage/sinval.h"
#include "tcop/fastpath.h"
#include "tcop/pquery.h"
#include "tcop/tcopprot.h"
@ -1899,6 +1900,7 @@ die(SIGNAL_ARGS)
/* until we are done getting ready for it */
InterruptHoldoffCount++;
DisableNotifyInterrupt();
DisableCatchupInterrupt();
/* Make sure CheckDeadLock won't run while shutting down... */
LockWaitCancel();
InterruptHoldoffCount--;
@ -1955,6 +1957,7 @@ StatementCancelHandler(SIGNAL_ARGS)
if (LockWaitCancel())
{
DisableNotifyInterrupt();
DisableCatchupInterrupt();
InterruptHoldoffCount--;
ProcessInterrupts();
}
@ -2006,6 +2009,7 @@ ProcessInterrupts(void)
QueryCancelPending = false; /* ProcDie trumps QueryCancel */
ImmediateInterruptOK = false; /* not idle anymore */
DisableNotifyInterrupt();
DisableCatchupInterrupt();
ereport(FATAL,
(errcode(ERRCODE_ADMIN_SHUTDOWN),
errmsg("terminating connection due to administrator command")));
@ -2015,6 +2019,7 @@ ProcessInterrupts(void)
QueryCancelPending = false;
ImmediateInterruptOK = false; /* not idle anymore */
DisableNotifyInterrupt();
DisableCatchupInterrupt();
ereport(ERROR,
(errcode(ERRCODE_QUERY_CANCELED),
errmsg("canceling query due to user request")));
@ -2595,9 +2600,8 @@ PostgresMain(int argc, char *argv[], const char *username)
* midst of output during who-knows-what operation...
*/
pqsignal(SIGPIPE, SIG_IGN);
pqsignal(SIGUSR1, SIG_IGN); /* this signal available for use */
pqsignal(SIGUSR2, Async_NotifyHandler); /* flush also sinval cache */
pqsignal(SIGUSR1, CatchupInterruptHandler);
pqsignal(SIGUSR2, NotifyInterruptHandler);
pqsignal(SIGFPE, FloatExceptionHandler);
/*
@ -2761,6 +2765,7 @@ PostgresMain(int argc, char *argv[], const char *username)
disable_sig_alarm(true);
QueryCancelPending = false; /* again in case timeout occurred */
DisableNotifyInterrupt();
DisableCatchupInterrupt();
debug_query_string = NULL;
/*
@ -2879,6 +2884,7 @@ PostgresMain(int argc, char *argv[], const char *username)
* signal */
EnableNotifyInterrupt();
EnableCatchupInterrupt();
/* Allow "die" interrupt to be processed while waiting */
ImmediateInterruptOK = true;
@ -2901,6 +2907,7 @@ PostgresMain(int argc, char *argv[], const char *username)
QueryCancelPending = false; /* forget any CANCEL signal */
DisableNotifyInterrupt();
DisableCatchupInterrupt();
/*
* (5) check for any other interesting events that happened while