> -----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 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? Thanks Zhihong
