[dpdk-users] OVS vs OVS-DPDK
Avi Cohen (A)
avi.cohen at huawei.com
Wed May 24 15:51:36 CEST 2017
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 at intel.com]
> Sent: Wednesday, 24 May, 2017 4:23 PM
> To: Avi Cohen (A)
> Cc: users at dpdk.org
> Subject: Re: [dpdk-users] OVS vs OVS-DPDK
>
>
> > On May 24, 2017, at 3:29 AM, Avi Cohen (A) <avi.cohen at 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
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