Bug 185

Summary:	PVP zero-loss performance degradation without --legacy-mem
Product:	DPDK	Reporter:	Maxime Coquelin (maxime.coquelin)
Component:	core	Assignee:	Maxime Coquelin (maxime.coquelin)
Status:	CONFIRMED ---
Severity:	normal	CC:	ajit.khaparde, anatoly.burakov, echaudro
Priority:	Normal
Version:	18.05
Target Milestone:	---
Hardware:	All
OS:	All

Description Maxime Coquelin 2019-01-10 11:52:59 CET

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

Comment 1 Maxime Coquelin 2019-01-10 11:55:10 CET

Note that the issue is seen starting v18.05, but is reproduced with DPDK v18.11 LTS.

Comment 2 Anatoly Burakov 2019-01-10 12:27:41 CET

Does it by any chance depend on IOVA contiguousness? And what is the IOVA mode when running these?

Comment 3 Ajit Khaparde 2020-09-16 23:53:35 CEST

Maxime, IS this still an issue? If yes, can you respond to Anatoly's questions? Thanks