From 4de82f7d7c50a81ec8e70e2cb0ab413ab9134c0b Mon Sep 17 00:00:00 2001 From: Simon Riggs Date: Sun, 13 Nov 2011 09:00:57 +0000 Subject: Wakeup WALWriter as needed for asynchronous commit performance. Previously we waited for wal_writer_delay before flushing WAL. Now we also wake WALWriter as soon as a WAL buffer page has filled. Significant effect observed on performance of asynchronous commits by Robert Haas, attributed to the ability to set hint bits on tuples earlier and so reducing contention caused by clog lookups. --- src/backend/access/transam/xlog.c | 33 ++++++++++++++++++++++++++++++++- 1 file changed, 32 insertions(+), 1 deletion(-) (limited to 'src/backend/access/transam/xlog.c') diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 0d494e2e3bf..20c04240b70 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -432,6 +432,11 @@ typedef struct XLogCtlData */ Latch recoveryWakeupLatch; + /* + * WALWriterLatch is used to wake up the WALWriter to write some WAL. + */ + Latch WALWriterLatch; + /* * During recovery, we keep a copy of the latest checkpoint record here. * Used by the background writer when it wants to create a restartpoint. @@ -1916,19 +1921,35 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch) } /* - * Record the LSN for an asynchronous transaction commit/abort. + * Record the LSN for an asynchronous transaction commit/abort + * and nudge the WALWriter if there is a complete page to write. * (This should not be called for for synchronous commits.) */ void XLogSetAsyncXactLSN(XLogRecPtr asyncXactLSN) { + XLogRecPtr WriteRqstPtr = asyncXactLSN; + /* use volatile pointer to prevent code rearrangement */ volatile XLogCtlData *xlogctl = XLogCtl; SpinLockAcquire(&xlogctl->info_lck); + LogwrtResult = xlogctl->LogwrtResult; if (XLByteLT(xlogctl->asyncXactLSN, asyncXactLSN)) xlogctl->asyncXactLSN = asyncXactLSN; SpinLockRelease(&xlogctl->info_lck); + + /* back off to last completed page boundary */ + WriteRqstPtr.xrecoff -= WriteRqstPtr.xrecoff % XLOG_BLCKSZ; + + /* if we have already flushed that far, we're done */ + if (XLByteLE(WriteRqstPtr, LogwrtResult.Flush)) + return; + + /* + * Nudge the WALWriter if we have a full page of WAL to write. + */ + SetLatch(&XLogCtl->WALWriterLatch); } /* @@ -5072,6 +5093,7 @@ XLOGShmemInit(void) XLogCtl->Insert.currpage = (XLogPageHeader) (XLogCtl->pages); SpinLockInit(&XLogCtl->info_lck); InitSharedLatch(&XLogCtl->recoveryWakeupLatch); + InitSharedLatch(&XLogCtl->WALWriterLatch); /* * If we are not in bootstrap mode, pg_control should already exist. Read @@ -10013,3 +10035,12 @@ WakeupRecovery(void) { SetLatch(&XLogCtl->recoveryWakeupLatch); } + +/* + * Manage the WALWriterLatch + */ +Latch * +WALWriterLatch(void) +{ + return &XLogCtl->WALWriterLatch; +} -- cgit v1.2.3