On 11/04/2016 01:30 PM, Wang, Zhihong wrote: > > >> -----Original Message----- >> From: Maxime Coquelin [mailto:maxime.coquelin at redhat.com] >> Sent: Friday, November 4, 2016 7:23 PM >> To: Wang, Zhihong <zhihong.wang at intel.com>; Yuanhan Liu >> <yuanhan.liu at linux.intel.com> >> Cc: stephen at networkplumber.org; Pierre Pfister (ppfister) >> <ppfister at cisco.com>; Xie, Huawei <huawei.xie at intel.com>; dev at >> dpdk.org; >> vkaplans at redhat.com; mst at 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
