On 22 September 2016 at 18:04, Wang, Zhihong <zhihong.wang at intel.com> wrote: > > >> -----Original Message----- >> From: Jianbo Liu [mailto:jianbo.liu at linaro.org] >> Sent: Thursday, September 22, 2016 5:02 PM >> To: Wang, Zhihong <zhihong.wang at intel.com> >> Cc: Yuanhan Liu <yuanhan.liu at linux.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 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 > > > > I think your number is little bit hard to understand for me, this patch's > optimization contains 2 parts: > > 1. ring operation: works for both mrg_rxbuf on and off > > 2. remote write ordering: works for mrg_rxbuf=on only > > So, for mrg_rxbuf=off, if this patch is good for 64B packets, then it > shouldn't do anything bad for larger packets. > > This is the gain on x86 platform: host iofwd between nic and vhost, > guest rxonly. > > nic2vm enhancement > 64 21.83% > 128 16.97% > 256 6.34% > 512 0.01% > 1024 0.00% > I bootup a VM with 2 virtual port, and stress the traffic between them. First, I stressed with pktgen-dpdk in VM, and did iofwd in host. Then, as you told, I did rxonly in VM, and txonly in host.
> I suspect there's some complication in ARM's micro-arch. > > Could you try v6 and apply all patches except the the last one: > [PATCH v6 6/6] vhost: optimize cache access > > And see if there's still perf drop? > The last patch can improve the performance. The drop is actually caused by the second patch. Jianbo
