From: Chris Wright <chrisw@sous-sol.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Mark McLoughlin <markmc@redhat.com>,
virtualization@lists.osdl.org, linux-kernel@vger.kernel.org,
Herbert Xu <herbert.xu@redhat.com>
Subject: Re: [PATCH 2/2] virtio_net: Improve the recv buffer allocation scheme
Date: Thu, 9 Oct 2008 08:35:46 -0700 [thread overview]
Message-ID: <20081009153546.GA6912@sequoia.sous-sol.org> (raw)
In-Reply-To: <200810091155.59731.rusty@rustcorp.com.au>
* Rusty Russell (rusty@rustcorp.com.au) wrote:
> On Thursday 09 October 2008 06:34:59 Mark McLoughlin wrote:
> > From: Herbert Xu <herbert.xu@redhat.com>
> >
> > If segmentation offload is enabled by the host, we currently allocate
> > maximum sized packet buffers and pass them to the host. This uses up
> > 20 ring entries, allowing us to supply only 20 packet buffers to the
> > host with a 256 entry ring. This is a huge overhead when receiving
> > small packets, and is most keenly felt when receiving MTU sized
> > packets from off-host.
>
> There are three approaches we should investigate before adding YA feature.
> Obviously, we can simply increase the number of ring entries.
Tried that, it didn't help much. I don't have my numbers handy, but
levelled off at about 512 and was a modest boost. It's still wasteful
to preallocate like that on the off-chance it's a large packet.
thanks,
-chris
next prev parent reply other threads:[~2008-10-09 15:35 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-08 19:34 [PATCH 1/2] virtio_net: Recycle some more rx buffer pages Mark McLoughlin
2008-10-08 19:34 ` [PATCH 2/2] virtio_net: Improve the recv buffer allocation scheme Mark McLoughlin
2008-10-09 0:55 ` Rusty Russell
2008-10-09 15:30 ` Herbert Xu
2008-10-09 17:40 ` Mark McLoughlin
2008-10-09 19:26 ` Anthony Liguori
2008-10-10 8:30 ` Mark McLoughlin
2008-10-16 9:15 ` Rusty Russell
2008-10-10 12:56 ` Mark McLoughlin
2008-10-16 4:43 ` Rusty Russell
2008-10-09 15:35 ` Chris Wright [this message]
2008-10-16 5:08 ` [PATCH 1/2] virtio_net: Recycle some more rx buffer pages Rusty Russell
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