On Wed, 2008-09-17 at 11:49 +0100, Mark McLoughlin wrote: > On Tue, 2008-09-16 at 22:24 +0300, Ben-Ami Yassour wrote: > > On Tue, 2008-09-16 at 09:16 -0500, Anthony Liguori wrote: > > > Ben-Ami Yassour wrote: > > > > I am running virtio with the latest KVM code, and see a significant > > > > performance issue. > > > > > > > > Ping to the host (or any other close machine) reports a 4ms delay. > > > > > > > > > > What kvm version and what host kernel version? > > > > > > It's very easy to mistakenly compile qemu without GSO support too. You > > > have to make sure that the 2.6.27 if_tun.h is being included by QEMU. > > > > Is there an option to control GSO support? How? > > GSO support is unconditionally enabled with model=virtio if > kvm-userspace is built with the correct kernel headers, the host kernel > supports tun/tap's IFF_VNET_HDR extension and if the guest supports GSO. How can we verify that GSO is actually used?
> GSO shouldn't affect ping latency - it should only affect throughput. > > I'd expect ping latency to be in the range of .15ms and .3ms since we > delay our reply for .15ms currently. > > Is this a regression? Have you tried bisecting it? > We are not sure yet what it is. We see very high variability in I/O rates, and have not yet found a combination of version, environment and parameters that shows good performance reliably. The head of the tree does show *bad* performance reliably. We are trying kvm-73 now. Thanks, Ben -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
