From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id C4761326B for ; Fri, 28 Oct 2016 09:42:17 +0200 (CEST) Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 173F480F93; Fri, 28 Oct 2016 07:42:17 +0000 (UTC) Received: from [10.36.7.170] (vpn1-7-170.ams2.redhat.com [10.36.7.170]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u9S7gDoX008186 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 28 Oct 2016 03:42:15 -0400 To: "Wang, Zhihong" , Yuanhan Liu References: <1474965769-24782-1-git-send-email-maxime.coquelin@redhat.com> <8F6C2BD409508844A0EFC19955BE09414E7CE6D1@SHSMSX103.ccr.corp.intel.com> <70cc3b89-d680-1519-add3-f38b228e65b5@redhat.com> <20161017132121.GG16751@yliu-dev.sh.intel.com> <8F6C2BD409508844A0EFC19955BE09414E7D8BDF@SHSMSX103.ccr.corp.intel.com> <20161027103317.GM16751@yliu-dev.sh.intel.com> <0ba8f8c9-2174-b3c1-4f07-f6911bffa6cd@redhat.com> <20161027104621.GN16751@yliu-dev.sh.intel.com> <8F6C2BD409508844A0EFC19955BE09414E7D90C7@SHSMSX103.ccr.corp.intel.com> From: Maxime Coquelin Message-ID: <88169067-290d-a7bb-ab2c-c9b8ec1b1ded@redhat.com> Date: Fri, 28 Oct 2016 09:42:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <8F6C2BD409508844A0EFC19955BE09414E7D90C7@SHSMSX103.ccr.corp.intel.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Fri, 28 Oct 2016 07:42:17 +0000 (UTC) Cc: "mst@redhat.com" , "dev@dpdk.org" , "vkaplans@redhat.com" Subject: Re: [dpdk-dev] [PATCH v4] vhost: Add indirect descriptors support to the TX path X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 28 Oct 2016 07:42:18 -0000 On 10/28/2016 02:49 AM, Wang, Zhihong wrote: > >> > -----Original Message----- >> > From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com] >> > Sent: Thursday, October 27, 2016 6:46 PM >> > To: Maxime Coquelin >> > Cc: Wang, Zhihong ; >> > stephen@networkplumber.org; Pierre Pfister (ppfister) >> > ; Xie, Huawei ; dev@dpdk.org; >> > vkaplans@redhat.com; mst@redhat.com >> > Subject: Re: [dpdk-dev] [PATCH v4] vhost: Add indirect descriptors support >> > to the TX path >> > >> > On Thu, Oct 27, 2016 at 12:35:11PM +0200, Maxime Coquelin wrote: >>> > > >>> > > >>> > > On 10/27/2016 12:33 PM, Yuanhan Liu wrote: >>>> > > >On Thu, Oct 27, 2016 at 11:10:34AM +0200, Maxime Coquelin wrote: >>>>> > > >>Hi Zhihong, >>>>> > > >> >>>>> > > >>On 10/27/2016 11:00 AM, Wang, Zhihong wrote: >>>>>> > > >>>Hi Maxime, >>>>>> > > >>> >>>>>> > > >>>Seems indirect desc feature is causing serious performance >>>>>> > > >>>degradation on Haswell platform, about 20% drop for both >>>>>> > > >>>mrg=on and mrg=off (--txqflags=0xf00, non-vector version), >>>>>> > > >>>both iofwd and macfwd. >>>>> > > >>I tested PVP (with macswap on guest) and Txonly/Rxonly on an Ivy >> > Bridge >>>>> > > >>platform, and didn't faced such a drop. >>>> > > > >>>> > > >I was actually wondering that may be the cause. I tested it with >>>> > > >my IvyBridge server as well, I saw no drop. >>>> > > > >>>> > > >Maybe you should find a similar platform (Haswell) and have a try? >>> > > Yes, that's why I asked Zhihong whether he could test Txonly in guest to >>> > > see if issue is reproducible like this. >> > >> > I have no Haswell box, otherwise I could do a quick test for you. IIRC, >> > he tried to disable the indirect_desc feature, then the performance >> > recovered. So, it's likely the indirect_desc is the culprit here. >> > >>> > > I will be easier for me to find an Haswell machine if it has not to be >>> > > connected back to back to and HW/SW packet generator. > In fact simple loopback test will also do, without pktgen. > > Start testpmd in both host and guest, and do "start" in one > and "start tx_first 32" in another. > > Perf drop is about 24% in my test. > Thanks, I never tried this test. I managed to find an Haswell platform (Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz), and can reproduce the problem with the loop test you mention. I see a performance drop about 10% (8.94Mpps/8.08Mpps). Out of curiosity, what are the numbers you get with your setup? As I never tried this test, I run it again on my Sandy Bridge setup, and I also see a performance regression, this time of 4%. If I understand correctly the test, only 32 packets are allocated, corresponding to a single burst, which is less than the queue size. So it makes sense that the performance is lower with this test case. Thanks, Maxime