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

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Message-Id: <da80025f-6942-615f-570e-5005a25eb147@linux.vnet.ibm.com>
Date:   Thu, 26 Oct 2017 13:53:12 -0400
From:   Matthew Rosato <mjrosato@...ux.vnet.ibm.com>
To:     Wei Xu <wexu@...hat.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


> 
> 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.

> 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