diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/transam/xlog.c | 66 |
1 files changed, 43 insertions, 23 deletions
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 7f518e0ba1b..6d4dc6940a5 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.285 2007/09/30 17:28:56 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.286 2007/10/12 19:39:59 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1332,6 +1332,40 @@ AdvanceXLInsertBuffer(bool new_segment) } /* + * Check whether we've consumed enough xlog space that a checkpoint is needed. + * + * Caller must have just finished filling the open log file (so that + * openLogId/openLogSeg are valid). We measure the distance from RedoRecPtr + * to the open log file and see if that exceeds CheckPointSegments. + * + * Note: it is caller's responsibility that RedoRecPtr is up-to-date. + */ +static bool +XLogCheckpointNeeded(void) +{ + /* + * A straight computation of segment number could overflow 32 + * bits. Rather than assuming we have working 64-bit + * arithmetic, we compare the highest-order bits separately, + * and force a checkpoint immediately when they change. + */ + uint32 old_segno, + new_segno; + uint32 old_highbits, + new_highbits; + + old_segno = (RedoRecPtr.xlogid % XLogSegSize) * XLogSegsPerFile + + (RedoRecPtr.xrecoff / XLogSegSize); + old_highbits = RedoRecPtr.xlogid / XLogSegSize; + new_segno = (openLogId % XLogSegSize) * XLogSegsPerFile + openLogSeg; + new_highbits = openLogId / XLogSegSize; + if (new_highbits != old_highbits || + new_segno >= old_segno + (uint32) (CheckPointSegments-1)) + return true; + return false; +} + +/* * Write and/or fsync the log at least as far as WriteRqst indicates. * * If flexible == TRUE, we don't have to write as far as WriteRqst, but @@ -1522,30 +1556,16 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch) /* * Signal bgwriter to start a checkpoint if we've consumed too - * much xlog since the last one. (We look at local copy of - * RedoRecPtr which might be a little out of date, but should - * be close enough for this purpose.) - * - * A straight computation of segment number could overflow 32 - * bits. Rather than assuming we have working 64-bit - * arithmetic, we compare the highest-order bits separately, - * and force a checkpoint immediately when they change. + * much xlog since the last one. For speed, we first check + * using the local copy of RedoRecPtr, which might be + * out of date; if it looks like a checkpoint is needed, + * forcibly update RedoRecPtr and recheck. */ - if (IsUnderPostmaster) + if (IsUnderPostmaster && + XLogCheckpointNeeded()) { - uint32 old_segno, - new_segno; - uint32 old_highbits, - new_highbits; - - old_segno = (RedoRecPtr.xlogid % XLogSegSize) * XLogSegsPerFile + - (RedoRecPtr.xrecoff / XLogSegSize); - old_highbits = RedoRecPtr.xlogid / XLogSegSize; - new_segno = (openLogId % XLogSegSize) * XLogSegsPerFile + - openLogSeg; - new_highbits = openLogId / XLogSegSize; - if (new_highbits != old_highbits || - new_segno >= old_segno + (uint32) (CheckPointSegments-1)) + (void) GetRedoRecPtr(); + if (XLogCheckpointNeeded()) RequestCheckpoint(CHECKPOINT_CAUSE_XLOG); } } |