>From 29b1954f4bba9ffd7e28fac1c8c4302dfe4bc2a6 Mon Sep 17 00:00:00 2001 From: Takashi Menjo Date: Mon, 10 Feb 2020 17:53:14 +0900 Subject: [msync 3/5] Lazy-unmap WAL segments --- src/backend/access/transam/xlog.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 43f9a8affc..317816a0b9 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -768,7 +768,9 @@ static const char *xlogSourceNames[] = {"any", "archive", "pg_wal", "stream"}; */ static int openLogFile = -1; static XLogSegNo openLogSegNo = 0; +static XLogSegNo beingClosedLogSegNo = 0; static char *mappedPages = NULL; +static char *beingUnmappedPages = NULL; static bool pmemMapped = 0; /* @@ -1162,6 +1164,14 @@ XLogInsertRecord(XLogRecData *rdata, } } + /* Lazy-unmap */ + if (beingUnmappedPages != NULL) + { + XLogFileUnmap(beingUnmappedPages, beingClosedLogSegNo); + beingUnmappedPages = NULL; + beingClosedLogSegNo = 0; + } + #ifdef WAL_DEBUG if (XLOG_DEBUG) { @@ -1794,9 +1804,23 @@ GetXLogBuffer(XLogRecPtr ptr) XLByteToSeg(ptr, segno, wal_segment_size); if (segno != openLogSegNo) { - /* Unmap the current segment if mapped */ + /* + * We do not want to unmap the current segment here because we are in + * a critial section and unmap is time-consuming operation. So we + * just mark it to be unmapped later. + */ if (mappedPages != NULL) - XLogFileUnmap(mappedPages, openLogSegNo); + { + /* + * If there is another being-unmapped segment, it cannot be helped; + * we unmap it here. + */ + if (beingUnmappedPages != NULL) + XLogFileUnmap(beingUnmappedPages, beingClosedLogSegNo); + + beingUnmappedPages = mappedPages; + beingClosedLogSegNo = openLogSegNo; + } /* Map the segment we need */ mappedPages = XLogFileMap(segno, &pmemMapped); -- 2.20.1