On 5/11/21 7:35 AM, Van Haaren, Harry wrote:
-----Original Message-----
From: Timothy Redaelli <[email protected]>
Sent: Monday, May 10, 2021 6:43 PM
To: Amber, Kumar <[email protected]>; [email protected]
Cc: [email protected]; [email protected]; [email protected]; Van Haaren, Harry
<[email protected]>
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.
See attached screentshoots for two samples --- master-0 and master-1
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.
EMC doing all the work --- see log below. This could explain why setting
avx512 is not helping.
NOTE: Our initial study showed that disabling EMC didn't help avx512
wining the case.
[root@netqe29 jhsiao]# ovs-appctl dpif-netdev/subtable-lookup-prio-get
Available lookup functions (priority : name)
0 : autovalidator
*1 : generic*
0 : avx512_gather
[root@netqe29 jhsiao]#
sleep 60; ovs-appctl dpif-netdev/pmd-perf-show
Time: 13:54:40.213
Measurement duration: 2242.679 s
pmd thread numa_id 0 core_id 24:
Iterations: 17531214131 (0.13 us/it)
- Used TSC cycles: 5816810246080 (100.1 % of total cycles)
- idle iterations: 17446464548 ( 84.1 % of used cycles)
- busy iterations: 84749583 ( 15.9 % of used cycles)
Rx packets: 2711982944 (1209 Kpps, 340 cycles/pkt)
Datapath passes: 2711982944 (1.00 passes/pkt)
- EMC hits: 2711677677 (100.0 %)
- SMC hits: 0 ( 0.0 %)
- Megaflow hits: 305261 ( 0.0 %, 1.00 subtbl lookups/hit)
- Upcalls: 6 ( 0.0 %, 0.0 us/upcall)
- Lost upcalls: 0 ( 0.0 %)
Tx packets: 2711982944 (1209 Kpps)
Tx batches: 84749583 (32.00 pkts/batch)
Time: 13:54:40.213
Measurement duration: 2242.675 s
pmd thread numa_id 0 core_id 52:
Iterations: 17529480287 (0.13 us/it)
- Used TSC cycles: 5816709563052 (100.1 % of total cycles)
- idle iterations: 17444555421 ( 84.1 % of used cycles)
- busy iterations: 84924866 ( 15.9 % of used cycles)
Rx packets: 2717592640 (1212 Kpps, 340 cycles/pkt)
Datapath passes: 2717592640 (1.00 passes/pkt)
- EMC hits: 2717280240 (100.0 %)
- SMC hits: 0 ( 0.0 %)
- Megaflow hits: 312362 ( 0.0 %, 1.00 subtbl lookups/hit)
- Upcalls: 6 ( 0.0 %, 0.0 us/upcall)
- Lost upcalls: 0 ( 0.0 %)
Tx packets: 2717592608 (1212 Kpps)
Tx batches: 84924866 (32.00 pkts/batch)
[root@netqe29 jhsiao]#
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
See avx512-0 and avx512-1 attachments.
4) "miniflow parser set study", I don't understand what is meant by "Failed to
converge"?
This is a 64-bytes 0-loss run. So, "Failed to converge" means the binary
search fail to get a meaningful Mpps value. This could be the case that
drops are happening --- could be 1 out of a million packets.
- 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/[email protected]/
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.
Tim, Can you answer this question?
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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