Machine details
CPU	8 core
OS	suse linux 10.3
RAM	24GB
Modified pgbench
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	15	shared buffers	2GB
Run1	242	145596	275	165617	13.63636	13.75106		record size	1800	update size	<50
Run2	238	146478	267	160753	12.18487	9.745491		threads	8	clients	16
Run3	238	143188	261	157665	9.663866	10.11048		ckpt seg	256	ckpt interval	15min
Avg	239.3333333	145087.3	267.6667	161345	11.83844	11.20543		wal page size	2K
pgbench	old code		Modified code		Difference(%)			Base records	1000000	fill factor	80
	TPS	Total	TPS	Total	TPS	Total		update	15	shared buffers	2GB
Run1	241	146070	257	154451	6.639004	5.73766		record size	1800	update size	<50
Run2	245	148590	269	163266	9.795918	9.876842		threads	8	clients	16
Run3	231	139062	247	149527	6.926407	7.52542		ckpt seg	256	ckpt interval	15min
Avg	239	144574	257.6667	155748	7.810321	7.728914		wal page size	2K