netdev - Re: [PATCH net] virtio_net: Avoid sending unnecessary vq coalescing commands

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Message-ID: <1722425431.2357254-1-hengqi@linux.alibaba.com>
Date: Wed, 31 Jul 2024 19:30:31 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org,
 "Michael S. Tsirkin" <mst@...hat.com>,
 Jason Wang <jasowang@...hat.com>,
 virtualization@...ts.linux.dev,
 EugenioPérez <eperezma@...hat.com>,
 "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH net] virtio_net: Avoid sending unnecessary vq coalescing commands

On Tue, 30 Jul 2024 18:20:20 -0700, Jakub Kicinski <kuba@...nel.org> wrote:
> On Mon, 29 Jul 2024 20:47:55 +0800 Heng Qi wrote:
> > Subject: [PATCH net] virtio_net: Avoid sending unnecessary vq coalescing commands
> 
> subject currently reads like this is an optimization, could you
> rephrase?

Jason's rephrase will be used.

> 
> > From the virtio spec:
> > 
> > 	The driver MUST have negotiated the VIRTIO_NET_F_VQ_NOTF_COAL
> > 	feature when issuing commands VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET
> > 	and VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET.
> > 
> > The driver must not send vq notification coalescing commands if
> > VIRTIO_NET_F_VQ_NOTF_COAL is not negotiated. This limitation of course
> > applies to vq resize.
> > 
> > Fixes: f61fe5f081cf ("virtio-net: fix the vq coalescing setting for vq resize")
> > Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
> > ---
> >  drivers/net/virtio_net.c | 29 +++++++++++++++++------------
> >  1 file changed, 17 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 0383a3e136d6..eb115e807882 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -3708,6 +3708,7 @@ static int virtnet_set_ringparam(struct net_device *dev,
> >  	u32 rx_pending, tx_pending;
> >  	struct receive_queue *rq;
> >  	struct send_queue *sq;
> > +	u32 pkts, usecs;
> >  	int i, err;
> >  
> >  	if (ring->rx_mini_pending || ring->rx_jumbo_pending)
> > @@ -3740,11 +3741,13 @@ static int virtnet_set_ringparam(struct net_device *dev,
> >  			 * through the VIRTIO_NET_CTRL_NOTF_COAL_TX_SET command, or, if the driver
> >  			 * did not set any TX coalescing parameters, to 0.
> >  			 */
> > -			err = virtnet_send_tx_ctrl_coal_vq_cmd(vi, i,
> > -							       vi->intr_coal_tx.max_usecs,
> > -							       vi->intr_coal_tx.max_packets);
> > -			if (err)
> > -				return err;
> > +			if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
> > +				usecs = vi->intr_coal_tx.max_usecs;
> > +				pkts = vi->intr_coal_tx.max_packets;
> > +				err = virtnet_send_tx_ctrl_coal_vq_cmd(vi, i, usecs, pkts);
> > +				if (err)
> > +					return err;
> 
> Can you check the feature inside the
> virtnet_send_.x_ctrl_coal_vq_cmd() helpers?
> 5 levels of indentation is a bit much

Makes sense. Will update in the next version.

Thanks.

> -- 
> pw-bot: cr