> -----Original Message----- > From: Maxime Coquelin [mailto:maxime.coquelin at redhat.com] > Sent: Friday, October 28, 2016 3:42 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 > > > > On 10/28/2016 02:49 AM, Wang, Zhihong wrote: > > > >> > -----Original Message----- > >> > From: Yuanhan Liu [mailto:yuanhan.liu at linux.intel.com] > >> > Sent: Thursday, October 27, 2016 6:46 PM > >> > To: Maxime Coquelin <maxime.coquelin at redhat.com> > >> > Cc: Wang, Zhihong <zhihong.wang at intel.com>; > >> > 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 > >> > > >> > 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?
Hi Maxime, Let's align our test case to RC2, mrg=on, loopback, on Haswell. My results below: 1. indirect=1: 5.26 Mpps 2. indirect=0: 6.54 Mpps It's about 24% drop. > > 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. Actually it's 32 burst, so 1024 packets in total, enough to fill the queue. Thanks Zhihong > > Thanks, > Maxime