From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH v4] vhost: Add indirect descriptors support to the TX path Date: Fri, 4 Nov 2016 13:54:00 +0100 Message-ID: <75d2c094-11e8-99aa-ccb5-60ded04047d7@redhat.com> References: <1474965769-24782-1-git-send-email-maxime.coquelin@redhat.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> <88169067-290d-a7bb-ab2c-c9b8ec1b1ded@redhat.com> <8F6C2BD409508844A0EFC19955BE09414E7DA533@SHSMSX103.ccr.corp.intel.com> <8F6C2BD409508844A0EFC19955BE09414E7DC40F@SHSMSX103.ccr.corp.intel.com> <17d285a9-818c-b060-8969-daccb052dc1f@redhat.com> <7e1c8953-db15-f377-cece-85cb7169bb17@redhat.com> <8F6C2BD409508844A0EFC19955BE09414E7DC5B6@SHSMSX103.ccr.corp.intel.com> <8F6C2BD409508844A0EFC19955BE09414E7DC66F@SHSMSX103.ccr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: "stephen@networkplumber.org" , "Pierre Pfister (ppfister)" , "Xie, Huawei" , "dev@dpdk.org" , "vkaplans@redhat.com" , "mst@redhat.com" To: "Wang, Zhihong" , Yuanhan Liu Return-path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 61D174A65 for ; Fri, 4 Nov 2016 13:54:06 +0100 (CET) In-Reply-To: <8F6C2BD409508844A0EFC19955BE09414E7DC66F@SHSMSX103.ccr.corp.intel.com> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 11/04/2016 01:30 PM, Wang, Zhihong wrote: > > >> -----Original Message----- >> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com] >> Sent: Friday, November 4, 2016 7:23 PM >> To: Wang, Zhihong ; Yuanhan Liu >> >> Cc: 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 >> >> >> >>>>>> Hi Maxime, >>>>>> >>>>>> I did a little more macswap test and found out more stuff here: >>>>> Thanks for doing more tests. >>>>> >>>>>> >>>>>> 1. I did loopback test on another HSW machine with the same H/W, >>>>>> and indirect_desc on and off seems have close perf >>>>>> >>>>>> 2. So I checked the gcc version: >>>>>> >>>>>> * Previous: gcc version 6.2.1 20160916 (Fedora 24) >>>>>> >>>>>> * New: gcc version 5.4.0 20160609 (Ubuntu 16.04.1 LTS) >>>>> >>>>> On my side, I tested with RHEL7.3: >>>>> - gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-11) >>>>> >>>>> It certainly contains some backports from newer GCC versions. >>>>> >>>>>> >>>>>> On previous one indirect_desc has 20% drop >>>>>> >>>>>> 3. Then I compiled binary on Ubuntu and scp to Fedora, and as >>>>>> expected I got the same perf as on Ubuntu, and the perf gap >>>>>> disappeared, so gcc is definitely one factor here >>>>>> >>>>>> 4. Then I use the Ubuntu binary on Fedora for PVP test, then the >>>>>> perf gap comes back again and the same with the Fedora binary >>>>>> results, indirect_desc causes about 20% drop >>>>> >>>>> Let me know if I understand correctly: >>> >>> Yes, and it's hard to breakdown further at this time. >>> >>> Also we may need to check whether it's caused by certain NIC >>> model. Unfortunately I don't have the right setup right now. >>> >>>>> Loopback test with macswap: >>>>> - gcc version 6.2.1 : 20% perf drop >>>>> - gcc version 5.4.0 : No drop >>>>> >>>>> PVP test with macswap: >>>>> - gcc version 6.2.1 : 20% perf drop >>>>> - gcc version 5.4.0 : 20% perf drop >>>> >>>> I forgot to ask, did you recompile only host, or both host and guest >>>> testmpd's in your test? >> >>> Both. >> >> I recompiled testpmd on a Fedora 24 machine using GCC6: >> gcc (GCC) 6.1.1 20160621 (Red Hat 6.1.1-3) >> Testing loopback with macswap on my Haswell RHEL7.3 machine gives me the >> following results: >> - indirect on: 7.75Mpps >> - indirect off: 7.35Mpps >> >> Surprisingly, I get better results with indirect on my setup (I >> reproduced the tests multiple times). >> >> Do you have a document explaining the tuning/config you apply to both >> the host and the guest (isolation, HT, hugepage size, ...) in your >> setup? > > > The setup where it goes wrong: > 1. Xeon E5-2699, HT on, turbo off, 1GB hugepage for both host and guest On the Haswell machine (on which I don't have BIOS access), HT is on, but I unplug siblings at runtime. I also have 1G pages on both sides, and I isolate the cores used by both testpmd and vCPUS. > 2. Fortville 40G > 3. Fedora 4.7.5-200.fc24.x86_64 > 4. gcc version 6.2.1 > 5. 16.11 RC2 for both host and guest > 6. PVP, testpmd macswap for both host and guest > > BTW, I do see indirect_desc gives slightly better performance for loopback > in tests on other platforms, but don't know how PVP performs yet. Interesting, other platforms are also Haswell/Broadwell? For PVP benchmarks, are your figures with 0% pkt loss? Thanks, Maxime > > >> >> Regards, >> Maxime