[ovs-discuss] OVS vs OVS-DPDK

Greg Rose gvrose8192 at gmail.com
Wed May 24 19:23:40 UTC 2017


On Wed, 2017-05-24 at 12:52 +0000, Avi Cohen (A) wrote:
> Thanks you Bhanuprakash for your reply.
> 
> I indeed use  vhost-user  interface for OVS-DPDK and vhost-net for standard OVS.
> Also saw this article in the link you've sent.
> But still try to find out the reasons for the boost performance with OVS-DPDK  (note that VMs  on both setup are unaware to OVS/OVS-DPDK which is running in the host)
> Also I found out that the bottleneck are the VMs and not the vswitch running in the host. 
> 
> These  reasons for  poor performance can be for example:
> 
> 1. number of packet copies in the path NIC - OVS - OS-guest-virtio - Application on guest
> 
> 2. interrupt upon receiving a packet
> 
> 3. # of context-switch / VM-exit
> etc..
> 
> I didn't see any info regarding these potential reasons on the docs.

Have you ever tried using perf?  It could help you identify performance
bottlenecks if that's what you're researching.

https://perf.wiki.kernel.org/index.php/Tutorial

Regards,

- Greg

> 
> Best Regards
> avi
> 
> > -----Original Message-----
> > From: Bodireddy, Bhanuprakash [mailto:bhanuprakash.bodireddy at intel.com]
> > Sent: Wednesday, 24 May, 2017 3:43 PM
> > To: Avi Cohen (A); ovs-discuss at openvswitch.org
> > Subject: RE: OVS vs OVS-DPDK
> > 
> > >Question:  what are the additional overhead in the standard OVS   that cause
> > >to poor performance related to the OVS-DPDK setup ?
> > >I'm not talking about  the PMD improvements (OVS-DPDK)  running on the
> > >host - but on overhead in the VM context in the standard OVS setup
> > 
> > When running guest instances on OvS, vhost-net driver modules shall be used.
> > In case of OvS-DPDK, vhost-user library is used and runs entirely in user space
> > and is the reason for higher performance in VM context Refer to this document
> > on some internals of vhost-library:
> > http://dpdk.readthedocs.io/en/v16.07/sample_app_ug/vhost.html
> > 
> > - Bhanuprakash.
> 
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