On Tue, 2010-05-04 at 21:34 +0200, Stefan Kaltenbrunner wrote:
> FWIW - I'm seeing a behaviour here under pgbench -S workloads that looks
> kinda related.
>
> using -j 16 -c 16 -T 120 I get either 100000tps and around 660000
> contextswitches per second or on some runs I end up with 150000tps and
> around 1M contextswitches/s sustained. I mostly get the 100k result but
> once in a while I get the 150k one. And one even can anticipate the
> final transaction rate from watching "vmstat 1"...
>
> I'm not sure yet on what is causing that behaviour but that is with
> 9.0B1 on a Dual Quadcore Nehalem box with 16 cpu threads (8+HT) on a
> pure in-memory workload (scale = 20 with 48GB RAM).
Educated guess at a fix: please test this patch. It's good for
performance testing, but doesn't work correctly at failover, which would
obviously be addressed prior to any commit.
--
Simon Riggs www.2ndQuadrant.com
*** a/src/backend/access/transam/xlog.c
--- b/src/backend/access/transam/xlog.c
***************
*** 158,163 **** static XLogRecPtr LastRec;
--- 158,164 ----
* known, need to check the shared state".
*/
static bool LocalRecoveryInProgress = true;
+ static bool KnownRecoveryState = false;
/*
* Local state for XLogInsertAllowed():
***************
*** 6524,6537 **** CheckRecoveryConsistency(void)
bool
RecoveryInProgress(void)
{
! /*
! * We check shared state each time only until we leave recovery mode. We
! * can't re-enter recovery, so there's no need to keep checking after the
! * shared variable has once been seen false.
! */
! if (!LocalRecoveryInProgress)
! return false;
! else
{
/* use volatile pointer to prevent code rearrangement */
volatile XLogCtlData *xlogctl = XLogCtl;
--- 6525,6533 ----
bool
RecoveryInProgress(void)
{
! if (KnownRecoveryState)
! return LocalRecoveryInProgress;
! else
{
/* use volatile pointer to prevent code rearrangement */
volatile XLogCtlData *xlogctl = XLogCtl;
***************
*** 6541,6546 **** RecoveryInProgress(void)
--- 6537,6544 ----
LocalRecoveryInProgress = xlogctl->SharedRecoveryInProgress;
SpinLockRelease(&xlogctl->info_lck);
+ KnownRecoveryState = true;
+
/*
* Initialize TimeLineID and RedoRecPtr when we discover that recovery
* is finished. InitPostgres() relies upon this behaviour to ensure
--
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