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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2005-12-06 18:10:06 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2005-12-06 18:10:06 +0000 |
| commit | a615acf555c0e9ea6ed1c5398d14b81ff2179e6c (patch) | |
| tree | 553e5845c030e029e955db1830eed3f8f695a09e /src/backend/access/transam/clog.c | |
| parent | 953208a34cbb7585ed4ae782141052461d35739b (diff) | |
| download | postgresql-a615acf555c0e9ea6ed1c5398d14b81ff2179e6c.tar.gz postgresql-a615acf555c0e9ea6ed1c5398d14b81ff2179e6c.zip | |
Arrange for read-only accesses to SLRU page buffers to take only a shared
lock, not exclusive, if the desired page is already in memory. This can
be demonstrated to be a significant win on the pg_subtrans cache when there
is a large window of open transactions. It should be useful for pg_clog
as well. I didn't try to make GetMultiXactIdMembers() use the code, as
that would have taken some restructuring, and what with the local cache
for multixact contents it probably wouldn't really make a difference.
Per my recent proposal.
Diffstat (limited to 'src/backend/access/transam/clog.c')
| -rw-r--r-- | src/backend/access/transam/clog.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c index 44e1b9b7d3b..22e2c0541e1 100644 --- a/src/backend/access/transam/clog.c +++ b/src/backend/access/transam/clog.c @@ -24,7 +24,7 @@ * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.34 2005/11/05 21:19:47 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.35 2005/12/06 18:10:06 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -128,9 +128,9 @@ TransactionIdGetStatus(TransactionId xid) char *byteptr; XidStatus status; - LWLockAcquire(CLogControlLock, LW_EXCLUSIVE); + /* lock is acquired by SimpleLruReadPage_ReadOnly */ - slotno = SimpleLruReadPage(ClogCtl, pageno, xid); + slotno = SimpleLruReadPage_ReadOnly(ClogCtl, pageno, xid); byteptr = ClogCtl->shared->page_buffer[slotno] + byteno; status = (*byteptr >> bshift) & CLOG_XACT_BITMASK; |