linux-kernel - Re: [net-next RFC V5 5/5] virtio_net: support negotiating the number of queues through ctrl vq

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Message-ID: <4FF65966.9040600@redhat.com>
Date:	Fri, 06 Jul 2012 11:20:06 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	Sasha Levin <levinsasha928@...il.com>
CC:	mst@...hat.com, mashirle@...ibm.com, krkumar2@...ibm.com,
	habanero@...ux.vnet.ibm.com, rusty@...tcorp.com.au,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, edumazet@...gle.com,
	tahm@...ux.vnet.ibm.com, jwhan@...ewood.snu.ac.kr,
	davem@...emloft.net, akong@...hat.com, kvm@...r.kernel.org,
	sri@...ibm.com
Subject: Re: [net-next RFC V5 5/5] virtio_net: support negotiating the number
 of queues through ctrl vq

On 07/05/2012 08:51 PM, Sasha Levin wrote:
> On Thu, 2012-07-05 at 18:29 +0800, Jason Wang wrote:
>> @@ -1387,6 +1404,10 @@ static int virtnet_probe(struct virtio_device *vdev)
>>          if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
>>                  vi->has_cvq = true;
>>
>> +       /* Use single tx/rx queue pair as default */
>> +       vi->num_queue_pairs = 1;
>> +       vi->total_queue_pairs = num_queue_pairs;
> The code is using this "default" even if the amount of queue pairs it
> wants was specified during initialization. This basically limits any
> device to use 1 pair when starting up.
>

Yes, currently the virtio-net driver would use 1 txq/txq by default 
since multiqueue may not outperform in all kinds of workload. So it's 
better to keep it as default and let user enable multiqueue by ethtool -L.

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