[ovs-dev] [v2 v2 0/6] MFEX Infrastructure + Optimizations

Van Haaren, Harry harry.van.haaren at intel.com
Tue May 11 11:35:06 UTC 2021


> -----Original Message-----
> From: Timothy Redaelli <tredaell at redhat.com>
> Sent: Monday, May 10, 2021 6:43 PM
> To: Amber, Kumar <kumar.amber at intel.com>; dev at openvswitch.org
> Cc: i.maximets at ovn.org; jhsiao at redhat.com; fbl at redhat.com; Van Haaren, Harry
> <harry.van.haaren at intel.com>
> Subject: Re: [ovs-dev] [v2 v2 0/6] MFEX Infrastructure + Optimizations

<snip patchset details for brevity>

> >
> 
> Hi,
> we (as Red Hat) did some tests with a "special" build created on top of
> master (a019868a6268 at that time) with with the 2 series ("DPIF
> Framework + Optimizations" and "MFEX Infrastructure + Optimizations")
> cherry-picked.
> The spec file was also modified in order to use add "-msse4.2 -mpopcnt"
> to OVS CFLAGS.

Hi Timothy,

Thanks for testing and reporting back your findings! Most of the configuration is clear to me, but I have a few open questions inline below for context.

The performance numbers reported in the email below do not show benefit when enabling AVX512, which contradicts our
recent whitepaper on benchmarking an Optimized Deployment of OVS, which includes the AVX512 patches you've benchmarked too.
Specifically Table 8. for DPIF/MFEX patches, and Table 9. for the overall optimizations at a platform level are relevant:
https://networkbuilders.intel.com/solutionslibrary/open-vswitch-optimized-deployment-benchmark-technology-guide

Based on the differences between these performance reports, there must be some discrepancy in our testing/measurements.
I hope that the questions below help us understand any differences so we can all measure the benefits from these optimizations.

Regards, -Harry


> RPM=openvswitch2.15-2.15.0-37.avx512.1.el8fdp (the "special" build with
> the patches backported)
> 
>    * Master --- 15.2 Mpps
>    * Plus "avx512_gather 3" Only --- 15.2 Mpps
>    * Plus "dpif-set dpif_avx512" Only --- 10.1 Mpps
>    * Plus "miniflow-parser-set study" --- Failed to converge
>    * Plus all three --- 13.5 Mpps

Open questions:
1) Is CPU frequency turbo enabled in any scenario, or always pinned to the 2.6 GHz base frequency?
   - A "perf top -C x,y"   (where x,y are datapath hyperthread ids) would be interesting to compare with 3) below.

2) "plus Avx512 gather 3" (aka, DPCLS in AVX512), we see same performance. Is DPCLS in use, or is EMC doing all the work?
   - The output of " ovs-appctl dpif-netdev/pmd-perf-show" would be interesting to understand where packets are classified. 

3) "dpif-set dpif_avx512" only. The performance here is very strange, with ~30% reduction, while our testing shows performance improvement.
   - A "perf top" here (compared vs step 1) would be helpful to see what is going on

4) "miniflow parser set study", I don't understand what is meant by "Failed to converge"?
   - Is the traffic running in your benchmark Ether()/IP()/UDP() ?
   - Note that the only traffic pattern accelerated today is Ether()/IP()/UDP() (see patch https://patchwork.ozlabs.org/project/openvswitch/patch/20210428091931.2090062-5-kumar.amber@intel.com/ for details). The next revision of the patchset will include other traffic patterns, for example Ether()/Dot1Q()/IP()/UDP() and Ether()/IP()/TCP().


> RPM=openvswitch2.15-2.15.0-15.el8fdp (w/o "-msse4.2 -mpopcnt")
>    * 15.2 Mpps

5) What CFLAGS "-march=" CPU ISA and "-O" optimization options are being used for the package?
   - It is likely that "-msse4.2 -mpopcnt" is already implied if -march=corei7 or Nehalem for example.



> P2P benchmark
>    * ovs-dpdk/25 Gb i40e <-> trex/i40e
>    * single queue two pmd's --- two HT's  out of a CPU core.
> 
> Host CPU
> Model name:          Intel(R) Xeon(R) Gold 6132 CPU @ 2.60GHz

Thanks for detailing the configuration, and looking forward to understanding the configuration/performance better.



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