From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zoltan Kiss Subject: Re: [PATCH net-next RFC 0/5] xen-netback: TX grant mapping instead of copy Date: Tue, 5 Nov 2013 17:01:15 +0000 Message-ID: <5279245B.6070202@citrix.com> References: <1383094220-14775-1-git-send-email-zoltan.kiss@citrix.com> <1383303035.672.29.camel@kazak.uk.xensource.com> <5273FA37.6020903@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Cc: , , , , To: Ian Campbell Return-path: In-Reply-To: <5273FA37.6020903@citrix.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 01/11/13 19:00, Zoltan Kiss wrote: > >> Based on my investigations the packet get only copied if it is > delivered to > >>Dom0 stack, which is due to this patch: > >>https://lkml.org/lkml/2012/7/20/363 > >>That's a bit unfortunate, but as far as I know for the huge majority > this use > >>case is not too important. >> Likely to be true, but it would still be interesting to know how badly >> this use case suffers with this change, and any increase in CPU usage >> would be interesting to know about as well. > I can't find my numbers, but as far as I remember it wasn't > significantly worse than grant copy. I will check that again. I've measured it now: with my patch it was 5.2 Gbps, without it 5.4. Both cases iperf in Dom0 maxed out its CPU, mostly in soft interrupt context, based on top. Zoli