Hi Pai, Thanks a lot. It helps. These patches allow ovs to decide to disable or enable AVX512 if I understand it correctly. Is it recommended to enable AVX512? AVX512 is enabled by default. It is disabled in DPDK because it is experimental. I wonder if I should disable it, it may cause performance worse.
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 _______________________________________________ discuss mailing list disc...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
