From: "Michael S. Tsirkin" <mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
Cc: Krishna Kumar <krkumar2-xthvdsQ13ZrQT0dZR+AlfA@public.gmane.org>,
Carsten Otte <cotte-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>,
lguest-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org,
Shirley Ma <xma-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>,
kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
habanero-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org,
Heiko Carstens
<heiko.carstens-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
steved-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org,
Christian Borntraeger
<borntraeger-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>,
Tom Lendacky
<tahm-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
Martin Schwidefsky
<schwidefsky-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>,
linux390-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org
Subject: Re: [PATCH RFC 2/3] virtio_net: fix tx capacity checks using new API
Date: Thu, 2 Jun 2011 16:28:52 +0300 [thread overview]
Message-ID: <20110602132852.GH7141@redhat.com> (raw)
In-Reply-To: <87vcwphtkd.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
On Thu, Jun 02, 2011 at 11:40:26AM +0930, Rusty Russell wrote:
> On Wed, 1 Jun 2011 12:49:54 +0300, "Michael S. Tsirkin" <mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 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.
I agree, it's unlikely.
s/still can't transmit anything/are still out of space and need to stop
the ring almost at once/
Better?
next prev parent reply other threads:[~2011-06-02 13:28 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
[not found] ` <cover.1306921434.git.mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-06-01 9:49 ` [PATCH RFC 1/3] virtio_ring: add capacity check API Michael S. Tsirkin
[not found] ` <8014f898ca6b768d7be626b83c617a1e84adfeb9.1306921434.git.mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-06-02 2:11 ` Rusty Russell
[not found] ` <87sjrthti1.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
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
[not found] ` <110045d5bf250e6ed9c739f8cc6adbbf54e3cc9c.1306921434.git.mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-06-02 2:10 ` Rusty Russell
[not found] ` <87vcwphtkd.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-06-02 13:28 ` Michael S. Tsirkin [this message]
2011-06-01 9:50 ` [PATCH RFC 3/3] virtio_net: limit xmit polling Michael S. Tsirkin
[not found] ` <1ec8eec325839ecf2eac9930a230361e7956047c.1306921434.git.mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-06-02 3:54 ` Rusty Russell
[not found] ` <87pqmwj3am.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-06-02 13:34 ` Michael S. Tsirkin
[not found] ` <20110602133425.GJ7141-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-06-02 14:17 ` Krishna Kumar2
[not found] ` <OF990F08C5.2ECE35B1-ON652578A3.004DC0FA-652578A3.004E3FE4-xthvdsQ13ZrQT0dZR+AlfA@public.gmane.org>
2011-06-02 14:43 ` Michael S. Tsirkin
[not found] ` <20110602144346.GA7995-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-06-02 15:26 ` Krishna Kumar2
[not found] ` <OFFF109303.D838CAE2-ON652578A3.0053357D-652578A3.00549366-xthvdsQ13ZrQT0dZR+AlfA@public.gmane.org>
2011-06-02 15:34 ` Michael S. Tsirkin
2011-06-03 4:08 ` Krishna Kumar2
2011-06-02 15:44 ` Michael S. Tsirkin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110602132852.GH7141@redhat.com \
--to=mst-h+wxahxf7alqt0dzr+alfa@public.gmane.org \
--cc=borntraeger-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org \
--cc=cotte-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org \
--cc=habanero-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org \
--cc=heiko.carstens-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org \
--cc=krkumar2-xthvdsQ13ZrQT0dZR+AlfA@public.gmane.org \
--cc=kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=lguest-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org \
--cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux390-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org \
--cc=netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org \
--cc=schwidefsky-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org \
--cc=steved-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org \
--cc=tahm-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org \
--cc=virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org \
--cc=xma-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).