On Tue, 21 Feb 2012 17:45:08 +0100, Dongsu Park <dongsu.park@xxxxxxxxxxxxxxxx> wrote: > Hi Rusty, > > On 13.02.2012 10:25, Rusty Russell wrote: > > On Fri, 10 Feb 2012 15:36:39 +0100, Dongsu Park <dongsu.park@xxxxxxxxxxxxxxxx> wrote: > > > Hi, > > > > > > 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. > > > > Interesting. There are two obvious possibilities here. One is that > > qemu has regressed, the other is that virtio_blk has regressed; the new > > qemu may negotiate new features. Please do the following in the guest > > with old and new qemus: > > > > cat /sys/class/block/vdb/device/features > > > > (eg, here that gives: 0010101101100000000000000000100e0). > > I did that on guest VM, using both qemu-kvm 0.14.1 and 1.0. > (cat /sys/class/block/vdb/device/features) > > using qemu-kvm 0.14.1: > > 0010101101100000000000000000100000000000000000000000000000000000 > > using qemu-kvm 1.0: > > 0010101101100000000000000000110000000000000000000000000000000000 > > >From my understanding, both of them have the same virtio features. > Please correct me if I'm wrong. Well, 1.0 supports event index (feature 29), but that's the only difference. This seems very much like a qemu regression. Thanks, Rusty. -- 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
