Move "hot" members of PGPROC into a separate PGXACT array.

This speeds up snapshot-taking and reduces ProcArrayLock contention.
Also, the PGPROC (and PGXACT) structures used by two-phase commit are
now allocated as part of the main array, rather than in a separate
array, and we keep ProcArray sorted in pointer order.  These changes
are intended to minimize the number of cache lines that must be pulled
in to take a snapshot, and testing shows a substantial increase in
performance on both read and write workloads at high concurrencies.

Pavan Deolasee, Heikki Linnakangas, Robert Haas

1 files changed, 2 insertions, 2 deletions

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index c151d3be191..c383011b5f6 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -981,7 +981,7 @@ RecordTransactionCommit(void)
 		 * bit fuzzy, but it doesn't matter.
 		 */
 		START_CRIT_SECTION();
-		MyProc->inCommit = true;
+		MyPgXact->inCommit = true;
 
 		SetCurrentTransactionStopTimestamp();
 
@@ -1155,7 +1155,7 @@ RecordTransactionCommit(void)
 	 */
 	if (markXidCommitted)
 	{
-		MyProc->inCommit = false;
+		MyPgXact->inCommit = false;
 		END_CRIT_SECTION();
 	}