Re: [dpdk-users] OVS vs OVS-DPDK

["Avi Cohen (A)" <avi.cohen@huawei.com>]

Thanks Keith for your reply

I found out that the bottleneck are the VMs and not the OVS/OVS-DPDK  running in the host.
VMs  on both setup are unaware to OVS/OVS-DPDK  and use their linux IP-stack. 
I found that the performance (e.g. throughput) between  VMa - OVS-DPDK  - network - OVS-DPDK - VMb  is much better than with  standard OVS.

I use vhost-user virtio for the OVS-DPDK setup to connect to VM ,  and vhost-net for the standard OVS

The  reasons for  standard OVS 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.

Best Regards
avi

> -----Original Message-----
> From: Wiles, Keith [mailto:keith.wiles@intel.com]
> Sent: Wednesday, 24 May, 2017 4:23 PM
> To: Avi Cohen (A)
> Cc: users@dpdk.org
> Subject: Re: [dpdk-users] OVS vs OVS-DPDK
> 
> 
> > On May 24, 2017, at 3:29 AM, Avi Cohen (A) <avi.cohen@huawei.com>
> wrote:
> >
> > Hello
> > Let me  ask it in a different way:
> > I want to understand the reasons for the  differences in performance between
> OVS-DPDK and standard OVS My setup is:  ovs/ovs-dpdk is running @ host
> communicating with a VM
> >
> > OVS-DPDK
> > 1. packet is received via physical port to the device.
> >
> > 2.DMA  transfer   to mempools on huge-pages  allocated by dpdk-ovs - in
> user-space.
> >
> > 3. OVS-DPDK  copies this packet to the shared-vring of the associated  guest
> (shared between ovs-dpdk userspace process and guest)
> >
> > 4. guest OS copies the packet to  userspace application on VM .
> >
> > Standard OVS
> >
> > 1. packet is received via physical port to the device.
> >
> > 2.packet is processed by the OVS and transferred to a virtio device connected
> to the VM - whar are the additional overhead here ?  QEMU processing  -
> translation , VM exit ??  other ?
> >
> > 3. guest OS copies the packet to  userspace application on VM .
> >
> >
> > 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
> 
> The primary reasons are OVS is not using DPDK and OVS is using the Linux
> kernel as well :-)
> 
> >
> > Best Regards
> > avi
> 
> Regards,
> Keith