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From: Rusty Russell <rusty@rustcorp•com.au>
To: Stephen Hemminger <stephen@networkplumber•org>,
	"Michael S. Tsirkin" <mst@redhat•com>,
	David Miller <davem@davemloft•net>
Cc: netdev@vger•kernel.org, virtualization@lists•linux-foundation.org
Subject: Re: [PATCH net-next] virtio: change comment in transmit
Date: Wed, 25 Mar 2015 14:29:38 +1030	[thread overview]
Message-ID: <87y4mlhglx.fsf@rustcorp.com.au> (raw)
In-Reply-To: <20150324162207.6d4ecf48@urahara>

Stephen Hemminger <stephen@networkplumber•org> writes:
> The original comment was not really informative or funny
> as well as sexist. Replace it with a better explanation of
> why the driver does stop and what the impacts are.
>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber•org>

Fair call.  Comment was certainly snarky, probably sexist.  I think it
expressed my feelings perfectly, however.

I note that there's still no comment saying "don't do this" in
netdevice.h; I gather returning NETDEV_TX_BUSY is still considered a Bad
Thing?

(Does it really BUG_ON?)

Thanks,
Rusty.

> --- a/drivers/net/virtio_net.c	2015-03-24 15:20:25.174671000 -0700
> +++ b/drivers/net/virtio_net.c	2015-03-24 16:17:28.478525333 -0700
> @@ -939,8 +939,12 @@ static netdev_tx_t start_xmit(struct sk_
>  	skb_orphan(skb);
>  	nf_reset(skb);
>  
> -	/* Apparently nice girls don't return TX_BUSY; stop the queue
> -	 * before it gets out of hand.  Naturally, this wastes entries. */
> +	/* It is better to stop queue if running out of space
> +	 * instead of forcing queuing layer to requeue the skb
> +	 * by returning TX_BUSY (and cause a BUG message).
> +	 * Since most packets only take 1 or 2 ring slots
> +	 * this means 16 slots are typically wasted.
> +	 */
>  	if (sq->vq->num_free < 2+MAX_SKB_FRAGS) {
>  		netif_stop_subqueue(dev, qnum);
>  		if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) {
> --
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next prev parent reply	other threads:[~2015-03-25  3:59 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-24 23:22 [PATCH net-next] virtio: change comment in transmit Stephen Hemminger
2015-03-25  1:23 ` David Miller
2015-03-25  3:59 ` Rusty Russell [this message]
2015-03-25  4:34   ` David Miller

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