[ovs-dev] [PATCH] netdev-dpdk: Enable INDIRECT_DESC on DPDK vHostUser.

O Mahony, Billy billy.o.mahony at intel.com
Mon Mar 20 11:18:31 UTC 2017


Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin [mailto:maxime.coquelin at redhat.com]
> Sent: Friday, March 17, 2017 9:48 AM
> To: O Mahony, Billy <billy.o.mahony at intel.com>; dev at openvswitch.org
> Subject: Re: [ovs-dev] [PATCH] netdev-dpdk: Enable INDIRECT_DESC on
> DPDK vHostUser.
> 
> Hi Billy,
> 
> On 03/01/2017 01:36 PM, Billy O'Mahony wrote:
> > Hi All,
> >
> > I'm creating this patch on the basis of performance results outlined
> > below. In summary it appears that enabling INDIRECT_DESC on DPDK
> > vHostUser ports leads to very large increase in performance when using
> > linux stack applications in the guest with no noticable performance
> > drop for DPDK based applications in the guest.
> >
> > Test#1 (VM-VM iperf3 performance)
> >  VMs use DPDK vhostuser ports
> >  OVS bridge is configured for normal action.
> >  OVS version 603381a (on 2.7.0 branch but before release,
> >      also seen on v2.6.0 and v2.6.1)
> >  DPDK v16.11
> >  QEMU v2.5.0 (also seen with v2.7.1)
> >
> >  Results:
> >   INDIRECT_DESC enabled    5.30 Gbit/s
> >   INDIRECT_DESC disabled   0.05 Gbit/s
> This is indeed a big gain.
> However, isn't there a problem when indirect descriptors are disabled?
> 0.05 Gbits/s is very low, no?

[[BO'M]] Yes the disabling of the indirect descriptors feature appears to be what causes the very low test result. And the root cause may actually be related to this bug https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1668829 . However, turning on the indirect descriptors certainly helps greatly. 

> 
> Could you share the iperf3 command line you used?

 [[BO'M]] In the server VM "iperf3 -s" and in the client "iperf3 -c <server ip addr> -t 30". -t 30 is the duration (secs) of the test. OVS-DPDK bridge was set to use normal action.

> 
> > Test#2  (Phy-VM-Phy RFC2544 Throughput)  DPDK PMDs are polling NIC,
> > DPDK loopback app running in guest.
> >  OVS bridge is configured with port forwarding to VM (via dpdkvhostuser
> ports).
> >  OVS version 603381a (on 2.7.0 branch but before release),
> >      other versions not tested.
> >  DPDK v16.11
> >  QEMU v2.5.0 (also seen with v2.7.1)
> >
> >  Results:
> >   INDIRECT_DESC enabled    2.75 Mpps @64B pkts (0.176 Gbit/s)
> >   INDIRECT_DESC disabled   2.75 Mpps @64B pkts (0.176 Gbit/s)
> 
> Is this with 0% packet loss?
[[BO'M]] Yes. To an accuracy of .05 Mpps. 
> 
> Regards,
> Maxime


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