From: Rusty Russell <rusty@rustcorp•com.au>
To: Krishna Kumar2 <krkumar2@in•ibm.com>
Cc: davem@davemloft•net, netdev@vger•kernel.org,
"Michael S. Tsirkin" <mst@redhat•com>
Subject: Re: [PATCH] virtio_net: Fix queue full check
Date: Fri, 29 Oct 2010 21:58:40 +1030 [thread overview]
Message-ID: <201010292158.40411.rusty@rustcorp.com.au> (raw)
In-Reply-To: <OF30574F6E.113EC5F4-ON652577CB.0037DAB5-652577CB.003BACE8@in.ibm.com>
On Fri, 29 Oct 2010 09:25:09 pm Krishna Kumar2 wrote:
> Rusty Russell <rusty@rustcorp•com.au> wrote on 10/29/2010 03:17:24 PM:
>
> > > Oct 17 10:22:40 localhost kernel: net eth0: Unexpected TX queue
> failure: -28
> > > Oct 17 10:28:22 localhost kernel: net eth0: Unexpected TX queue
> failure: -28
> > > Oct 17 10:35:58 localhost kernel: net eth0: Unexpected TX queue
> failure: -28
> > > Oct 17 10:41:06 localhost kernel: net eth0: Unexpected TX queue
> failure: -28
> > >
> > > I initially changed the check from -ENOMEM to -ENOSPC, but
> > > virtqueue_add_buf can return only -ENOSPC when it doesn't have
> > > space for new request. Patch removes redundant checks but
> > > displays the failure errno.
> > >
> > > Signed-off-by: Krishna Kumar <krkumar2@in•ibm.com>
> > > ---
> > > drivers/net/virtio_net.c | 15 ++++-----------
> > > 1 file changed, 4 insertions(+), 11 deletions(-)
> > >
> > > diff -ruNp org/drivers/net/virtio_net.c new/drivers/net/virtio_net.c
> > > --- org/drivers/net/virtio_net.c 2010-10-11 10:20:02.000000000 +0530
> > > +++ new/drivers/net/virtio_net.c 2010-10-21 17:37:45.000000000 +0530
> > > @@ -570,17 +570,10 @@ static netdev_tx_t start_xmit(struct sk_
> > >
> > > /* This can happen with OOM and indirect buffers. */
> > > if (unlikely(capacity < 0)) {
> > > - if (net_ratelimit()) {
> > > - if (likely(capacity == -ENOMEM)) {
> > > - dev_warn(&dev->dev,
> > > - "TX queue failure: out of memory\n");
> > > - } else {
> > > - dev->stats.tx_fifo_errors++;
> > > - dev_warn(&dev->dev,
> > > - "Unexpected TX queue failure: %d\n",
> > > - capacity);
> > > - }
> > > - }
> > > + if (net_ratelimit())
> > > + dev_warn(&dev->dev,
> > > + "TX queue failure (%d): out of memory\n",
> > > + capacity);
> >
> > Hold on... you were getting -ENOSPC, which shouldn't happen. What makes
> you
> > think it's out of memory?
>
> virtqueue_add_buf_gfp returns only -ENOSPC on failure, whether
> direct or indirect descriptors are used, so isn't -ENOSPC
> "expected"? (vring_add_indirect returns -ENOMEM on memory
> failure, but that is masked out and we go direct which is
> the failure point).
Ah, OK, gotchya.
I'm not even sure the fallback to linear makes sense; if we're failing
kmallocs we should probably just return -ENOMEM. Would mean we can
tell the difference between "out of space" (which should never happen
since we stop the queue when we have < 2+MAX_SKB_FRAGS slots left)
and this case.
Michael, what do you think?
Thanks,
Rusty.
next prev parent reply other threads:[~2010-10-29 11:28 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-28 5:10 [PATCH] virtio_net: Fix queue full check Krishna Kumar
2010-10-29 9:47 ` Rusty Russell
2010-10-29 10:55 ` Krishna Kumar2
2010-10-29 11:28 ` Rusty Russell [this message]
2010-11-02 16:17 ` Michael S. Tsirkin
2010-11-04 12:24 ` Michael S. Tsirkin
2010-11-04 16:17 ` Krishna Kumar2
2010-11-04 16:45 ` Michael S. Tsirkin
2010-11-07 23:08 ` Rusty Russell
2010-11-09 4:26 ` Krishna Kumar2
2010-11-09 13:15 ` Michael S. Tsirkin
2010-11-09 15:30 ` Krishna Kumar2
2010-11-09 15:30 ` Michael S. Tsirkin
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