netdev - [PATCH net-next] virtio: change comment in transmit

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Message-ID: <20150324162207.6d4ecf48@urahara>
Date:	Tue, 24 Mar 2015 16:22:07 -0700
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	David Miller <davem@...emloft.net>
Cc:	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: [PATCH net-next] virtio: change comment in transmit

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@...workplumber.org>

--- 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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