Re: [net-next rfc v7 1/3] virtio-net: separate fields of sending/receiving queue from virtnet_info

From: Jason Wang <jasowang@redhat.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: krkumar2@in.ibm.com, kvm@vger.kernel.org, mst@redhat.com,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	bhutchings@solarflare.com, jwhan@filewood.snu.ac.kr,
	shiyer@redhat.com
Subject: Re: [net-next rfc v7 1/3] virtio-net: separate fields of sending/receiving queue from virtnet_info
Date: Mon, 03 Dec 2012 13:15:01 +0800	[thread overview]
Message-ID: <3524590.ZWGua7A8ne@jason-thinkpad-t430s> (raw)
In-Reply-To: <87y5hfj3vl.fsf@rustcorp.com.au>

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On Monday, December 03, 2012 12:25:42 PM Rusty Russell wrote:
> Jason Wang <jasowang@redhat.com> writes:
> > To support multiqueue transmitq/receiveq, the first step is to separate
> > queue related structure from virtnet_info. This patch introduce
> > send_queue and receive_queue structure and use the pointer to them as the
> > parameter in functions handling sending/receiving.
> 
> OK, seems like a straightforward xform: a few nit-picks:
> > +/* Internal representation of a receive virtqueue */
> > +struct receive_queue {
> > +	/* Virtqueue associated with this receive_queue */
> > +	struct virtqueue *vq;
> > +
> > +        struct napi_struct napi;
> > +
> > +        /* Number of input buffers, and max we've ever had. */
> > +        unsigned int num, max;
> 
> Weird whitespace here.
> 

Oh, yes, will fix it.
> > +
> > +	/* Work struct for refilling if we run low on memory. */
> > +	struct delayed_work refill;
> 
> I can't really see the justificaiton for a refill per queue.  Just have
> one work iterate all the queues if it happens, unless it happens often
> (in which case, we need to look harder at this anyway).

But during this kind of iteration, we may need enable/disable the napi 
regardless of whether the receive queue has lots to be refilled. This may add 
extra latency. 
> 
> >  struct virtnet_info {
> >  
> >  	struct virtio_device *vdev;
> > 
> > -	struct virtqueue *rvq, *svq, *cvq;
> > +	struct virtqueue *cvq;
> > 
> >  	struct net_device *dev;
> >  	struct napi_struct napi;
> 
> You leave napi here, and take it away in the next patch.  I think it's
> supposed to go away now.

Yes, will remove it.

Thanks
> 
> Cheers,
> Rusty.
> --
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