[dpdk-dev] [Bug 185] PVP zero-loss performance degradation without --legacy-mem

[dpdk-dev] [Bug 185] PVP zero-loss performance degradation without --legacy-mem

[bugzilla]

https://bugs.dpdk.org/show_bug.cgi?id=185

            Bug ID: 185
           Summary: PVP zero-loss performance degradation without
                    --legacy-mem
           Product: DPDK
           Version: 18.05
          Hardware: All
                OS: All
            Status: CONFIRMED
          Severity: normal
          Priority: Normal
         Component: core
          Assignee: dev@dpdk.org
          Reporter: maxime.coquelin@redhat.com
  Target Milestone: ---

When doing PVP (Physical to Virtual to Physical) testing,
we measure a performance degradation when testpmd in guest
is launched without the --legacy-mem parameter.
P to V and V to P forwarding is done using OVS-DPDK on host side.

Without the --legacy-mem option, we get ~23% of line rate at 10G.
With the --legacy-mem option, we get ~29% of line rate at 10G.

1G hugepages are used both in host and guest.

Testpmd command line used in guest:
testpmd -c 7 -n 4 --socket-mem 2048 0 -w 0000:00:02.0 --legacy-mem -- --burst
64 -i --rxq=2 --txq=2 --rxd=4096 --txd=1024 --coremask=6 --auto-start
--port-topology=chained --forward-mode=macswap

testpmd -c 7 -n 4 --socket-mem 2048 0 -w 0000:00:02.0 -- --burst 64 -i --rxq=2
--txq=2 --rxd=4096 --txd=1024 --coremask=6 --auto-start --port-topology=chained
--forward-mode=macswap

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