netdev - Re: [rfc net-next v6 0/3] Multiqueue virtio-net

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Message-ID: <5090FE6B.4030001@redhat.com>
Date:	Wed, 31 Oct 2012 18:33:15 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	Rick Jones <rick.jones2@...com>
CC:	mst@...hat.com, davem@...emloft.net,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	rusty@...tcorp.com.au, krkumar2@...ibm.com, kvm@...r.kernel.org
Subject: Re: [rfc net-next v6 0/3] Multiqueue virtio-net

On 10/31/2012 03:05 AM, Rick Jones wrote:
> On 10/30/2012 03:03 AM, Jason Wang wrote:
>> Hi all:
>>
>> This series is an update version of multiqueue virtio-net driver 
>> based on
>> Krishna Kumar's work to let virtio-net use multiple rx/tx queues to 
>> do the
>> packets reception and transmission. Please review and comments.
>>
>> Changes from v5:
>> - Align the implementation with the RFC spec update v4
>> - Switch the mode between single mode and multiqueue mode without reset
>> - Remove the 256 limitation of queues
>> - Use helpers to do the mapping between virtqueues and tx/rx queues
>> - Use commbined channels instead of separated rx/tx queus when do the 
>> queue
>> number configuartion
>> - Other coding style comments from Michael
>>
>> Reference:
>> - A protype implementation of qemu-kvm support could by found in
>> git://github.com/jasowang/qemu-kvm-mq.git
>> - V5 could be found at http://lwn.net/Articles/505388/
>> - V4 could be found at https://lkml.org/lkml/2012/6/25/120
>> - V2 could be found at http://lwn.net/Articles/467283/
>> - Michael virtio-spec: 
>> http://www.spinics.net/lists/netdev/msg209986.html
>>
>> Perf Numbers:
>>
>> - Pktgen test shows the receiving capability of the multiqueue 
>> virtio-net were
>>    dramatically improved.
>> - Netperf result shows latency were greately improved according to 
>> the test
>> result.
>
> I suppose it is technically correct to say that latency was improved, 
> but usually for aggregate request/response tests I tend to talk about 
> the aggregate transactions per second.

Sure.
>
> Do you have a hypothesis as to why the improvement dropped going to 20 
> concurrent sessions from 10?
>
> rick jones 

I'm investigating this issuse currently, but with no much ideas. The 
aggregate transactions per second scales pretty well even with 20 
cocurrent sessions when doing test between a local host and a local vm. 
Looks like some bottleneck were reached when doing testing over 10gb or 
vms as even if I increase the number of sessions, the result would not 
increase.
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