On Mon, Jun 21, 2010 at 12:13:49PM +0930, Rusty Russell wrote:
> On Fri, 11 Jun 2010 04:33:43 am Michael S. Tsirkin wrote:
> > > > > @@ -572,12 +571,14 @@ again:
> > > > >
> > > > > /* This can happen with OOM and indirect buffers. */
> > > > > if (unlikely(capacity < 0)) {
> > > > > - netif_stop_queue(dev);
> > > > > - dev_warn(&dev->dev, "Unexpected full queue\n");
> > > > > - if (unlikely(!virtqueue_enable_cb(vi->svq))) {
> > > > > - virtqueue_disable_cb(vi->svq);
> > > > > - netif_start_queue(dev);
> > > > > - goto again;
> > > > > + if (net_ratelimit()) {
> > > > > + if (likely(capacity == -ENOMEM))
> > > > > + dev_warn(&dev->dev,
> > > > > + "TX queue failure: out of memory\n");
> > > > > + else
> > > > > + dev_warn(&dev->dev,
> > > > > + "Unexpected TX queue failure: %d\n",
> > > > > + capacity);
> ...
> >
> > Well, I only keep the existing behaviour around.
>
> Actually, it *does* change behavior, as the comment indicates. So let's
> fix the whole thing. AFAICT wth TX_BUSY we'll get called again RSN, and
> that's not really useful for OOM.
>
> This is what I have:
>
> Subject: virtio_net: fix oom handling on tx
> Date: Thu, 10 Jun 2010 18:20:41 +0300
> From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
>
> virtio net will never try to overflow the TX ring, so the only reason
> add_buf may fail is out of memory. Thus, we can not stop the
> device until some request completes - there's no guarantee anything
> at all is outstanding.
>
> Make the error message clearer as well: error here does not
> indicate queue full.
>
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> (...and avoid TX_BUSY)
> Cc: stable@xxxxxxxxxx
> ---
> drivers/net/virtio_net.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -562,7 +562,6 @@ static netdev_tx_t start_xmit(struct sk_
> struct virtnet_info *vi = netdev_priv(dev);
> int capacity;
>
> -again:
> /* Free up any pending old buffers before queueing new ones. */
> free_old_xmit_skbs(vi);
>
> @@ -571,14 +570,17 @@ again:
>
> /* This can happen with OOM and indirect buffers. */
> if (unlikely(capacity < 0)) {
> - netif_stop_queue(dev);
> - dev_warn(&dev->dev, "Unexpected full queue\n");
> - if (unlikely(!virtqueue_enable_cb(vi->svq))) {
> - virtqueue_disable_cb(vi->svq);
> - netif_start_queue(dev);
> - goto again;
> + if (net_ratelimit()) {
> + if (likely(capacity == -ENOMEM))
> + dev_warn(&dev->dev,
> + "TX queue failure: out of memory\n");
> + else
> + dev_warn(&dev->dev,
> + "Unexpected TX queue failure: %d\n",
> + capacity);
> }
> - return NETDEV_TX_BUSY;
> + kfree_skb(skb);
> + return NETDEV_TX_OK;
If we do so, let's increment the dropped counter and/or error counter?
> }
> virtqueue_kick(vi->svq);
>
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