Hi Martin, On 05.03.2012 17:13, Martin Mailand wrote: > Am 10.02.2012 15:36, schrieb Dongsu Park: > >Recently I observed performance regression regarding virtio-blk, > >especially different IO bandwidths between qemu-kvm 0.14.1 and 1.0. > >So I want to share the benchmark results, and ask you what the reason > >would be. > > > Hi, > I think I found the problem, there is no regression in the code. > I think the problem is, that qmeu-kvm with the IO-Thread enabled > doesn't produce enough cpu load to get the core to a higher cpu > frequency, because the load is distributed to two threads. > If I change the cpu governor to "performance" the result from the > master branch is better than from the v0.14.1 branch. > I get the same results on a serversystem without powermanagment activated. > > @Dongsu Could you confirm those findings? Yes, I can confirm that. I just tested with different CPU governor configs, "ondemand" and "performance". (qemu-kvm 1.0, AMD Phenom II X4 955) The result is more or less like yours. Bandwidth with "performance" gets more than 100% better than that with "ondemand". That looks definitely one of the reasons of regressions I experienced. Actually I had always tested with "ondemand", which I haven't noticed. Good catch, thanks! Dongsu > 1. Test on i7 Laptop with Cpu governor "ondemand". > > v0.14.1 > bw=63492KB/s iops=15873 > bw=63221KB/s iops=15805 > > v1.0 > bw=36696KB/s iops=9173 > bw=37404KB/s iops=9350 > > master > bw=36396KB/s iops=9099 > bw=34182KB/s iops=8545 > > Change the Cpu governor to "performance" > master > bw=81756KB/s iops=20393 > bw=81453KB/s iops=20257 > > > 2. Test on AMD Istanbul without powermanagement activated. > > v0.14.1 > bw=53167KB/s iops=13291 > bw=61386KB/s iops=15346 > > v1.0 > bw=43599KB/s iops=10899 > bw=46288KB/s iops=11572 > > master > bw=60678KB/s iops=15169 > bw=62733KB/s iops=15683 > > -martin -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
