netdev - Re: Regression in throughput between kvm guests over virtual bridge

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Message-ID: <20171031070717.wcbgrp6thrjmtrh3@Wei-Dev>
Date:   Tue, 31 Oct 2017 15:07:17 +0800
From:   Wei Xu <wexu@...hat.com>
To:     Matthew Rosato <mjrosato@...ux.vnet.ibm.com>
Cc:     Jason Wang <jasowang@...hat.com>, mst@...hat.com,
        netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: Regression in throughput between kvm guests over virtual bridge

On Thu, Oct 26, 2017 at 01:53:12PM -0400, Matthew Rosato wrote:
> 
> > 
> > Are you using the same binding as mentioned in previous mail sent by you? it
> > might be caused by cpu convention between pktgen and vhost, could you please
> > try to run pktgen from another idle cpu by adjusting the binding? 
> 
> I don't think that's the case -- I can cause pktgen to hang in the guest
> without any cpu binding, and with vhost disabled even.

Yes, I did a test and it also hangs in guest, before we figure it out,
maybe you try udp with uperf with this case?

VM   -> Host
Host -> VM
VM   -> VM

> 
> > BTW, did you see any improvement when running pktgen from the host if no 
> > regression was found? Since this can be reproduced with only 1 vcpu for
> > guest, may you try this bind? This might help simplify the problem.
> >   vcpu0  -> cpu2
> >   vhost  -> cpu3
> >   pktgen -> cpu1 
> > 
> 
> Yes -- I ran the pktgen test from host to guest with the binding
> described.  I see an approx 5% increase in throughput from 4.12->4.13.
> Some numbers:
> 
> host-4.12: 1384486.2pps 663.8MB/sec
> host-4.13: 1434598.6pps 688.2MB/sec

That's great, at least we are aligned in this case.

Jason, any thoughts on this? 

Wei

>