Red Hat Bugzilla – Bug 653972
qcow2: Backport performance related patches
Last modified: 2013-01-09 18:20:43 EST
RHEL 6.0 suffers from qcow2 being slow, especially during cluster allocations. Upstream has got a number of improvements since then, which need to be backported. They include patches to reduce the number of cache flushes (for cluster allocation) as well as avoiding bounce buffers in the usual read/write paths (should help with already allocated clusters, too).
Benchmark iozone test with qemu-kvm-0.12.1.2-2.113.el6.x86_64(rhel6.0)and qemu-kvm-0.12.1.2-2.152.el6.x86_64 (rhel6.1)and the results was the average of 3 iterations. iozone ci: incache:iozone -a -i 0 -i 1 -s ${incache}k -r 64k -w -+u -R ./test -f /mnt/t1 dio:iozone -a -i 0 -i 1 -s ${incache}k -r 64k -I -w -+u -R ./test -f /mnt/t2 outcache:iozone -a -i 0 -i 1 -s ${outcache}k -r 64k -w -+u -R ./test -f /mnt/t3 Qcow2-local qcow2 cache=none elevator=deadline Type Rhel6.0-virtio Rhel6.1-virtio Improvement% Dio-Write 2982.33 111403.67 3635.46% Dio-Rewrite 126111.67 127007.33 0.71% Dio-Read 152177.33 148669.67 -2.30% Dio-Reread 153957 151804 -1.40% Incache-Write 33806.33 176658.67 422.56% Incache-ReWrite 153125 179184.67 17.02% Incache-Read 224914.67 995947 342.81% Incache-Reread 608146.67 980144.67 61.17% Out-of-Cache-Write 28324.67 156221 451.54% Out-of-Cache-ReWrite 131248.67 156416 19.18% Out-of-Cache-Read 122599 149164 21.67% Out-of-Cache-Reread 121197 148777.33 22.76% Qcow2-nfs qcow2 cache=none elevator=dealine Type Rhel6.0-virtio Rhel6.1-virtio Improvement% Dio-Write 43287 55643.33 28.55% Dio-Rewrite 62998.67 60435 -4.07% Dio-Read 58227.67 57521.67 -1.21% Dio-Reread 58375 57936.33 -0.75% Incache-Write 105898 133944.67 26.48% Incache-ReWrite 131408 93042 -29.20% Incache-Read 194638.33 956375.67 391.36% Incache-Reread 577811.67 810256.33 40.23% Out-of-Cache-Write 90921.67 100638 10.69% Out-of-Cache-ReWrite 93297.33 76711.67 -17.78% Out-of-Cache-Read 53543 58324.33 8.93% Out-of-Cache-Reread 64981.33 83918 29.14% From results,we could see qcow2 has been gotten highly improvements from dio-wirte,incache-write ,incache-Read,Out-of-Cache-Write Out-of-Cache-Reread secnarios. So it's pass.~~
According comment #7 ,change the bus status to verified.thanks~~
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-0534.html