On Wed, May 20, 2020 at 3:35 AM Federico Iezzi <[email protected]> wrote: > > > > > > On Wed, 20 May 2020 at 12:20, Van Haaren, Harry <[email protected]> > wrote: >> >> > -----Original Message----- >> > From: William Tu <[email protected]> >> > Sent: Wednesday, May 20, 2020 1:12 AM >> > To: Van Haaren, Harry <[email protected]> >> > Cc: [email protected]; [email protected] >> > Subject: Re: [ovs-dev] [PATCH v2 5/5] dpif-lookup: add avx512 gather >> > implementation >> > >> > On Mon, May 18, 2020 at 9:12 AM Van Haaren, Harry >> > <[email protected]> wrote: >> > > >> > > > -----Original Message----- >> > > > From: William Tu <[email protected]> >> > > > Sent: Monday, May 18, 2020 3:58 PM >> > > > To: Van Haaren, Harry <[email protected]> >> > > > Cc: [email protected]; [email protected] >> > > > Subject: Re: [ovs-dev] [PATCH v2 5/5] dpif-lookup: add avx512 gather >> > > > implementation >> > > > >> > > > On Wed, May 06, 2020 at 02:06:09PM +0100, Harry van Haaren wrote: >> > > > > This commit adds an AVX-512 dpcls lookup implementation. >> > > > > It uses the AVX-512 SIMD ISA to perform multiple miniflow >> > > > > operations in parallel. >> >> <snip lots of code/patch contents for readability> >> >> > Hi Harry, >> > >> > I managed to find a machine with avx512 in google cloud and did some >> > performance testing. I saw lower performance when enabling avx512, > > > AVX512 instruction path lowers the clock speed well below the base frequency > [1]. > Aren't you killing the PMD performance while improving the lookup ones? > > [1] > https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/2nd-gen-xeon-scalable-spec-update.pdf > (see page 20) >
Hi Federico, Thanks for sharing the link. Does that mean if OVS PMD uses avx512 on one core, then all the other cores's frequency will be lower? There are some discussion here: https://lemire.me/blog/2018/09/07/avx-512-when-and-how-to-use-these-new-instructions/ My take is that overall down clocking will happen, but application will get better performance. William _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
