> -----Original Message----- > From: Yuanhan Liu [mailto:yuanhan.liu at linux.intel.com] > Sent: Tuesday, September 27, 2016 6:21 PM > To: Jianbo Liu <jianbo.liu at linaro.org> > Cc: Wang, Zhihong <zhihong.wang at intel.com>; Maxime Coquelin > <maxime.coquelin at redhat.com>; dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue > > On Thu, Sep 22, 2016 at 05:01:41PM +0800, Jianbo Liu wrote: > > On 22 September 2016 at 14:58, Wang, Zhihong <zhihong.wang at intel.com> > wrote: > > > > > > > > >> -----Original Message----- > > >> From: Jianbo Liu [mailto:jianbo.liu at linaro.org] > > >> Sent: Thursday, September 22, 2016 1:48 PM > > >> To: Yuanhan Liu <yuanhan.liu at linux.intel.com> > > >> Cc: Wang, Zhihong <zhihong.wang at intel.com>; Maxime Coquelin > > >> <maxime.coquelin at redhat.com>; dev at dpdk.org > > >> Subject: Re: [dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue > > >> > > >> On 22 September 2016 at 10:29, Yuanhan Liu <yuanhan.liu at > > >> linux.intel.com> > > >> wrote: > > >> > On Wed, Sep 21, 2016 at 08:54:11PM +0800, Jianbo Liu wrote: > > >> >> >> > My setup consists of one host running a guest. > > >> >> >> > The guest generates as much 64bytes packets as possible using > > >> >> >> > > >> >> >> Have you tested with other different packet size? > > >> >> >> My testing shows that performance is dropping when packet size is > > >> more > > >> >> >> than 256. > > >> >> > > > >> >> > > > >> >> > Hi Jianbo, > > >> >> > > > >> >> > Thanks for reporting this. > > >> >> > > > >> >> > 1. Are you running the vector frontend with mrg_rxbuf=off? > > >> >> > > > >> Yes, my testing is mrg_rxbuf=off, but not vector frontend PMD. > > >> > > >> >> > 2. Could you please specify what CPU you're running? Is it Haswell > > >> >> > or Ivy Bridge? > > >> >> > > > >> It's an ARM server. > > >> > > >> >> > 3. How many percentage of drop are you seeing? > > >> The testing result: > > >> size (bytes) improvement (%) > > >> 64 3.92 > > >> 128 11.51 > > >> 256 24.16 > > >> 512 -13.79 > > >> 1024 -22.51 > > >> 1500 -12.22 > > >> A correction is that performance is dropping if byte size is larger than > > >> 512. > > > > > > > > > Jianbo, > > > > > > Could you please verify does this patch really cause enqueue perf to drop? > > > > > > You can test the enqueue path only by set guest to do rxonly, and compare > > > the mpps by show port stats all in the guest. > > > > > > > > Tested with testpmd, host: txonly, guest: rxonly > > size (bytes) improvement (%) > > 64 4.12 > > 128 6 > > 256 2.65 > > 512 -1.12 > > 1024 -7.02 > > There is a difference between Zhihong's code and the old I spotted in > the first time: Zhihong removed the avail_idx prefetch. I understand > the prefetch becomes a bit tricky when mrg-rx code path is considered; > thus, I didn't comment on that. > > That's one of the difference that, IMO, could drop a regression. I then > finally got a chance to add it back. > > A rough test shows it improves the performance of 1400B packet size greatly > in the "txonly in host and rxonly in guest" case: +33% is the number I get > with my test server (Ivybridge).
Thanks Yuanhan! I'll validate this on x86. > > I guess this might/would help your case as well. Mind to have a test > and tell me the results? > > BTW, I made it in rush; I haven't tested the mrg-rx code path yet. > > Thanks. > > --yliu
