netdev - Re: [V2 RFC net-next PATCH 2/2] virtio_net: export more statistics through ethtool

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Message-ID: <20120608070237.GA32532@redhat.com>
Date:	Fri, 8 Jun 2012 10:02:37 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	netdev@...r.kernel.org, rusty@...tcorp.com.au,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [V2 RFC net-next PATCH 2/2] virtio_net: export more statistics
 through ethtool

On Fri, Jun 08, 2012 at 11:35:25AM +0800, Jason Wang wrote:
> >>>  @@ -655,7 +695,17 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> >>>    		kfree_skb(skb);
> >>>    		return NETDEV_TX_OK;
> >>>    	}
> >>>  -	virtqueue_kick(vi->svq);
> >>>  +
> >>>  +	kick = virtqueue_kick_prepare(vi->svq);
> >>>  +	if (unlikely(kick))
> >>>  +		virtqueue_notify(vi->svq);
> >>>  +
> >>>  +	u64_stats_update_begin(&stats->syncp);
> >>>  +	if (unlikely(kick))
> >>>  +		stats->data[VIRTNET_TX_KICKS]++;
> >>>  +	stats->data[VIRTNET_TX_Q_BYTES] += skb->len;
> >>>  +	stats->data[VIRTNET_TX_Q_PACKETS]++;
> >is this statistic interesting?
> >how about decrementing when we free?
> >this way we see how many are pending..
> >
> 
> Currently we didn't have per-vq statistics but per-cpu, so the skb
> could be sent by one vcpu and freed by another.
> Pehaps another reason to use per-queue satistics.

For transmit, it could be done easily as we both send and free skbs
under a lock. I'm not sure how acceptable it is to
take a lock in get_stats but send a separate patch like this
and we'll see what others say.

-- 
MST
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