Machine details
CPU	8 core
OS	suse linux 10.3
RAM	24GB
Modified pgbench
one char, one varchar and one integer update
pgbench	old code		Modified code		Difference(%)			Base records	1000000	fill factor	100
	TPS	Total	TPS	Total	TPS	Total		update	3	shared buffers	2GB
Run1	1237	743032	1386	832450	12.04527	12.03421		record size	1800	update size	250
Run2	1020	612983	1368	822133	34.11765	34.12003		threads	8	clients	16
Run3	959	576783	1371	826621	42.96142	43.31577		auto vacuum	off	wal page size	1K
Avg	1072	644266	1375	827068	28.26493	28.37368		ckpt seg	256	ckpt interval	15min
								sync commit	off
pgbench	old code		Modified code		Difference(%)			Base records	1000000	fill factor	80
	TPS	Total	TPS	Total	TPS	Total		update	3	shared buffers	2GB
Run1	1443	866768	2670	1604341	85.03119	85.09463		record size	1800	update size	250
Run2	1342	806624	2639	1587127	96.6468	96.76169		threads	8	clients	16
Run3	1505	905615	2869	1724974	90.63123	90.47542		auto vacuum	off	wal page size	1K
Avg	1430	859669	2726	1638814	90.62937	90.63314		ckpt seg	256	ckpt interval	15min
								sync commit	off