From: Rusty Russell <rusty@rustcorp.com.au>
To: "Michael S. Tsirkin" <mst@redhat.com>, linux-kernel@vger.kernel.org
Cc: Carsten Otte <cotte@de.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
linux390@de.ibm.com, Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Shirley Ma <xma@us.ibm.com>,
lguest@lists.ozlabs.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-s390@vger.kernel.org,
kvm@vger.kernel.org, Krishna Kumar <krkumar2@in.ibm.com>,
Tom Lendacky <tahm@linux.vnet.ibm.com>,
steved@us.ibm.com, habanero@linux.vnet.ibm.com
Subject: Re: [PATCH RFC 2/3] virtio_net: fix tx capacity checks using new API
Date: Thu, 02 Jun 2011 11:40:26 +0930 [thread overview]
Message-ID: <87vcwphtkd.fsf@rustcorp.com.au> (raw)
In-Reply-To: <110045d5bf250e6ed9c739f8cc6adbbf54e3cc9c.1306921434.git.mst@redhat.com>
On Wed, 1 Jun 2011 12:49:54 +0300, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> In the (rare) case where new descriptors are used
> while virtio_net enables vq callback for the TX vq,
> virtio_net uses the number of sg entries in the skb it frees to
> calculate how many descriptors in the ring have just been made
> available. But this value is an overestimate: with indirect buffers
> each skb only uses one descriptor entry, meaning we may wake the queue
> only to find we still can't transmit anything.
This is a bit misleading.
The value is an overestimate, but so is the requirement for
2+MAX_SKB_FRAGS, *unless* we suddenly drop into direct mode due to OOM.
Thanks,
Rusty.
next prev parent reply other threads:[~2011-06-02 3:55 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-01 9:49 [PATCH RFC 0/3] virtio and vhost-net capacity handling Michael S. Tsirkin
2011-06-01 9:49 ` [PATCH RFC 1/3] virtio_ring: add capacity check API Michael S. Tsirkin
2011-06-02 2:11 ` Rusty Russell
2011-06-02 13:30 ` Michael S. Tsirkin
2011-06-01 9:49 ` [PATCH RFC 2/3] virtio_net: fix tx capacity checks using new API Michael S. Tsirkin
2011-06-02 2:10 ` Rusty Russell [this message]
2011-06-02 13:28 ` Michael S. Tsirkin
2011-06-01 9:50 ` [PATCH RFC 3/3] virtio_net: limit xmit polling Michael S. Tsirkin
2011-06-02 3:54 ` Rusty Russell
2011-06-02 13:34 ` Michael S. Tsirkin
2011-06-02 14:17 ` Krishna Kumar2
2011-06-02 14:43 ` Michael S. Tsirkin
2011-06-02 15:26 ` Krishna Kumar2
2011-06-02 15:34 ` Michael S. Tsirkin
2011-06-03 4:08 ` Krishna Kumar2
2011-06-02 15:44 ` Michael S. Tsirkin
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