io latency on Xen x86

test cnt:	12579738
[Total ] min:	14973	avg:	21510
[IO IN ] min:	3246	avg:	10335
[IO OUT] min:	6303	avg:	11175

[root@DomU1 DomU1 ~]$cat /proc/iolat
test cnt:	52419739
[Total ] min:	15066	avg:	20144
[IO IN ] min:	3870	avg:	9719
[IO OUT] min:	6135	avg:	10424

[root@DomU1 DomU1 ~]$cat /proc/iolat
test cnt:	16319903
[Total ] min:	13221	avg:	20454
[IO IN ] min:	2739	avg:	9610
[IO OUT] min:	5730	avg:	10844