On Thu, Jun 2, 2022 at 7:31 PM Pai G, Sunil <sunil.pa...@intel.com> wrote: > > Hi Li, > > My responses are inline. > > Thanks and Regards, > Sunil > > > -----Original Message----- > > From: Li Zhang <zhlci...@gmail.com> > > Sent: Thursday, June 2, 2022 9:56 PM > > To: Pai G, Sunil <sunil.pa...@intel.com> > > Cc: ovs-discuss@openvswitch.org > > Subject: Re: [ovs-discuss] One question about AVX512 support > > > > Hi Pai, > > > > Thanks a lot. It helps. > > These patches allow ovs to decide to disable or enable AVX512 if I > > understand it correctly. > > Well,...not quite, they simply remove the dependency on DPDK i.e > the decision to use AVX512/not in OVS is left to OVS only [DPDK arch > options/flags are simply ignored]. >
I see. > > Is it recommended to enable AVX512? AVX512 is enabled by default. > > To get better performance and make the most out of the features offered by > the platform, I would say so, yes. > > > It is disabled in DPDK because it is experimental. > > I would recommend enabling AVX-512 in DPDK as well. > Here is a link which describes how to: > https://doc.dpdk.org/guides/howto/avx512.html > > i.e for ovs, use the following command before launching vswitchd: > ovs-vsctl --no-wait set Open_vSwitch . > other_config:dpdk-extra="--force-max-simd-bitwidth=512" > > > > I wonder if I should disable it, it may cause performance worse. > > Here are few links I have handy that describe the performance improvements > seen with AVX-512 along with its impacts. > https://networkbuilders.intel.com/solutionslibrary/open-vswitch-optimized-deployment-benchmark-technology-guide > . > https://networkbuilders.intel.com/intel-technologies/3rd-gen-intel-xeon-scalable-processors-experience-kits > , Acceleration section. > > I would encourage you to go through these links. > Really really thanks. It's very useful. I need to look at it. > > > > > Thanks > > Li > > > > On Thu, Jun 2, 2022 at 4:00 PM Pai G, Sunil <sunil.pa...@intel.com> wrote: > > > > > > Hi Li, > > > > > > The assumption of ovs being dependent on dpdk for avx512 might not be > > true. > > > I found these two commits below in ovs-2.14.2 which strips out the "- > > march" and "-mno-avx512f" flags exported by dpdk i.e removes dependency on > > DPDK. The reason for this is rightly mentioned below as well. Hope this > > helps. > > > > > > > > > commit bb8f0e2a810889241f1d886d160ccee9b96c4d63 > > > Author: Ian Stokes <ian.sto...@intel.com> > > > Date: Fri Jan 15 15:46:02 2021 +0000 > > > > > > acinclude: Strip out -mno-avx512f provided by DPDK. > > > > > > DPDK forces '-mno-avx512f' flag for the application if the toolchain > > > used to build DPDK had broken AVX512 support. > > > > > > DPDK forces '-mno-avx512f' flag for the application if the toolchain > > > used to build DPDK had broken AVX512 support. But OVS could be > > built > > > with a completely different or fixed toolchain with correct avx512 > > > support. > > > > > > Fix that by stripping out `-mno-avx512f` as we already do for '- > > march'. > > > This will allow the OVS to decide if the AVX512 can be used. > > > > > > Reordering of CFLAGS (i.e. adding DPDK flags before OVS ones) is not > > an > > > option since autotools might reorder them back later and it's very > > > unpredictable. > > > > > > Reported-at: https://github.com/openvswitch/ovs-issues/issues/201 > > > Signed-off-by: Ilya Maximets <i.maxim...@ovn.org> > > > Co-authored-by: Ilya Maximets <i.maxim...@ovn.org> > > > Signed-off-by: Ian Stokes <ian.sto...@intel.com> > > > > > > commit e9f9104d00006a83ce7efd702120171835991779 > > > Author: Ian Stokes <ian.sto...@intel.com> > > > Date: Fri Jan 15 14:54:04 2021 +0000 > > > > > > acinclude: Strip out -march provided by DPDK. > > > > > > DPDK flags may include -march. Forcing -march could be > > > considered too heavy a requirement when users compile OVS from > > > source and could override user provided options. > > > > > > Resolve this by stripping -march from provided DPDK flags. > > > > > > Signed-off-by: Ian Stokes <ian.sto...@intel.com> > > > > > > > > > > > > Thanks and Regards, > > > Sunil > > > > > > > -----Original Message----- > > > > From: discuss <ovs-discuss-boun...@openvswitch.org> On Behalf Of Li > > > > Zhang > > > > Sent: Thursday, June 2, 2022 6:35 PM > > > > To: ovs-discuss@openvswitch.org > > > > Subject: [ovs-discuss] One question about AVX512 support > > > > > > > > Hi all, > > > > > > > > We are using openvswitch 2.14.2, and dpdk-19.11.4. I found avx512 is > > > > enabled by default but it's disabled in DPDK. But I think ovs is > > > > dependent on the dpdk library, right? But why does ovs work with > > > > avx512 disabled in DPDK? > > > > > > > > I am not quite sure about the relationship between OVS and DPDK, any > > > > suggestions? > > > > > > > > -- > > > > > > > > Best Regards > > > > -Li > > > > _______________________________________________ > > > > discuss mailing list > > > > disc...@openvswitch.org > > > > https://mail.openvswitch.org/mailman/listinfo/ovs-discuss > > > > > > > > -- > > > > Best Regards > > -Li -- Best Regards -Li _______________________________________________ discuss mailing list disc...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
