From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH 0/7] AlacrityVM guest drivers Date: Fri, 07 Aug 2009 10:46:24 -0500 Message-ID: <4A7C4C50.5040503@codemonkey.ws> References: <20090803171030.17268.26962.stgit@dev.haskins.net> <20090806081955.GA9752@redhat.com> <4A7C37E5.4040302@codemonkey.ws> <4A7C42C8.5050608@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Michael S. Tsirkin" , Gregory Haskins , linux-kernel@vger.kernel.org, alacrityvm-devel@lists.sourceforge.net, netdev@vger.kernel.org, kvm@vger.kernel.org To: Gregory Haskins Return-path: In-Reply-To: <4A7C42C8.5050608@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Gregory Haskins wrote: > That said, note that the graphs were from earlier kernel runs (2.6.28, > 29-rc8). The most recent data I can find that I published is for > 2.6.29, announced with the vbus-v3 release back in April: > > http://lkml.org/lkml/2009/4/21/408 > > In it, the virtio-net throughput numbers are substantially higher and > possibly more in line with your expectations (4.5gb/s) (though notably > still lagging venet, which weighed in at 5.6gb/s). > Okay, that makes more sense. Would be nice to update the graphs as they make virtio look really, really bad :-) > Generally, I find that the virtio-net exhibits non-deterministic results > from release to release. I suspect (as we have discussed) the > tx-mitigation scheme. Some releases buffer the daylights out of the > stream, and virtio gets close(r) throughput (e.g. 4.5g vs 5.8g, but > absolutely terrible latency (4000us vs 65us). Other releases it seems > to operate with more of a compromise (1.3gb/s vs 3.8gb/s, but 350us vs > 85us). > Are you using kvm modules or a new kernel? There was some timer infrastructure changes around 28/29 and it's possible that the system your on is now detecting an hpet which will result in a better time source. That could have an affect on mitigation. > If there is another patch-series/tree I should be using for comparison, > please point me at it. > No, I think it's fair to look at upstream Linux. Looking at the latest bits would be nice though because there are some virtio friendly changes recently like MSI-x and GRO. Since you're using the latest vbus bits, it makes sense to compare against the latest virtio bits. Regards, Anthony Liguori