From mboxrd@z Thu Jan 1 00:00:00 1970 From: annie li Subject: Re: [PATCH V4 0/3] xen-netback: switch to NAPI + kthread 1:1 model Date: Fri, 23 Aug 2013 10:24:38 +0800 Message-ID: <5216C7E6.5090306@oracle.com> References: <1375779963-24090-1-git-send-email-wei.liu2@citrix.com> <20130806131637.GS2924@reaktio.net> <5200FA3A.4030704@citrix.com> <5201058A.4070307@citrix.com> <20130822151238.GA6881@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20130822151238.GA6881@zion.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Wei Liu Cc: ian.campbell@citrix.com, xen-devel@lists.xen.org, David Vrabel , msw@amazon.com, Andrew Bennieston List-Id: xen-devel@lists.xenproject.org On 2013-8-22 23:12, Wei Liu wrote: > On Tue, Aug 06, 2013 at 03:17:46PM +0100, Andrew Bennieston wrote: >> On 06/08/13 14:29, David Vrabel wrote: >>> On 06/08/13 14:16, Pasi K=E4rkk=E4inen wrote: >>>> On Tue, Aug 06, 2013 at 10:06:00AM +0100, Wei Liu wrote: >>>>> IRQs are distributed to 4 cores by hand in the new model, while in the >>>>> old model vifs are automatically distributed to 4 kthreads. >>>>> >>>> Hmm.. so with these patches applied is is *required* to do manual conf= iguration in dom0 to get good performance? >>> This should be irqbalanced's job. The existing version doesn't do a >>> good enough job yet though. Andrew Bennieston may have more details. >>> >>> David >>> >> irqbalance 1.0.6 [1] includes a patch [2] from Wei Liu [3] that adds >> support for balancing `xen-dyn-event' interrupts. When I have compiled >> this version and run it under Xen(Server) I noticed that the >> interrupts are indeed moving between cores, but not necessarily in >> what I would call an obvious or optimal way (e.g. several VIF >> interrupts are being grouped onto a single dom0 VCPU at times). I plan >> on investigating this further when time permits. >> >> I also noticed that, from time to time, the irqbalance process >> disappears. I tracked this down to a segfault that occurs when a VM >> shuts down and an IRQ disappears during one of irqbalance's periodic >> rescans. I'm hoping to be able to narrow this down sufficiently to >> identify the cause and ideally fix it, but I don't have a lot of time >> to work on this at the moment. >> >> As for the impact on Wei's patches, without irqbalance it would be >> trivial to automatically assign (via a script, on VM start) the >> interrupts for a particular VIF to a particular dom0 vCPU in a >> round-robin fashion, just as VIFs were previously assigned to netback >> kthreads. This would result in broadly the same performance as before, >> while an improved irqbalanced should give better performance and >> fairness when two different VIFs would otherwise be competing for the >> same resources. >> > So can I conclude that this model doesn't incur severe performance > regression, on the other hand it has its advantage on fairness so it's > worth upstreaming? I agree. From Andrew's result, I do not see any bad affect about this model, and = well worked irqbalance may give us much better performance too. And this can also simplify persistent map patch(it is kind of stopped, = but my recent test shows some good results) > > If so I will post another series shortly with all comments addressed. Please go ahead. Thanks Annie