From mboxrd@z Thu Jan 1 00:00:00 1970 From: Asias He Subject: Re: [PATCH v2 3/4] kvm tools: Use ioeventfd in virtio-net Date: Wed, 01 Jun 2011 19:11:46 +0800 Message-ID: <4DE61E72.6010503@gmail.com> References: <1306513120-28794-1-git-send-email-levinsasha928@gmail.com> <1306513120-28794-3-git-send-email-levinsasha928@gmail.com> <4DE42DEE.8070906@gmail.com> <1306859577.25406.19.camel@lappy> <4DE598DC.90502@gmail.com> <1306910151.2929.7.camel@lappy> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Pekka Enberg , john@jfloren.net, kvm@vger.kernel.org, mingo@elte.hu, gorcunov@gmail.com, prasadjoshi124@gmail.com To: Sasha Levin Return-path: Received: from mail-px0-f179.google.com ([209.85.212.179]:40546 "EHLO mail-px0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758756Ab1FALNT (ORCPT ); Wed, 1 Jun 2011 07:13:19 -0400 Received: by pxi2 with SMTP id 2so3667596pxi.10 for ; Wed, 01 Jun 2011 04:13:19 -0700 (PDT) In-Reply-To: <1306910151.2929.7.camel@lappy> Sender: kvm-owner@vger.kernel.org List-ID: On 06/01/2011 02:35 PM, Sasha Levin wrote: > On Wed, 2011-06-01 at 09:41 +0800, Asias He wrote: >> On 06/01/2011 12:32 AM, Sasha Levin wrote: >>> On Tue, 2011-05-31 at 10:18 +0300, Pekka Enberg wrote: >>>> On Tue, May 31, 2011 at 2:53 AM, Asias He wrote: >>>>> TAP based network performance with ioeventfd >>>> >>>> Heh, so how did it look _before_ ioeventfd? Did performance improve >>>> and how much? >>> >>> Asias, did you use TCP or UDP values as bandwidth in your previous test? >>> >> >> These commit log have the performance test result before ioeventfd. But >> the UDP one is missing. >> >> commit 739ddbb3b0fe52aa90a84727a6e90da37ce7661b >> commit 4ed38b41fc034cfb51fec2004f523fe98faa27f6 >> >> >> Netpef test shows this patch changes: >> >> the host to guest bandwidth >> from 2866.27 Mbps (cpu 33.96%) to 5548.87 Mbps (cpu 53.87%), >> >> the guest to host bandwitdth >> form 1408.86 Mbps (cpu 99.9%) to 1301.29 Mbps (cpu 99.9%). >> >> >> Anyway, I did another test and post the result here: >> >> Test shows host -> guest TCP performance drops from 6736.04 to 5562.25. >> guest -> host TCP performance dumps from 1572.51 to 1731.55. > > That's quite strange. I wasn't expecting any changes with our current > network code: Our RX thread is blocking on readv() most of the time, so > it doesn't get affected by IRQ/ioeventfd signals at all, and the TX > thread should get signaled to wake up just once or twice when the stream > starts - after which the virtio ring should be full with data. > > I installed netperf and ran the tests (full results are below), guest -> > host TCP changed from 1862 to 2567 and host -> guest TCP changed from > 7716 to 8065. I have no idea why I am seeing this regression in my box. However, your change should not introduce this regression. -- Best Regards, Asias He