netdev - Re: [PATCH net-next] virtio_net: migrate mergeable rx buffers to page frag allocators

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Message-ID: <20131029191250.GE20848@redhat.com>
Date:	Tue, 29 Oct 2013 21:12:50 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	David Miller <davem@...emloft.net>
Cc:	eric.dumazet@...il.com, mwdalton@...gle.com,
	netdev@...r.kernel.org, edumazet@...gle.com, rusty@...tcorp.com.au,
	dborkman@...hat.com, virtualization@...ts.linux-foundation.org,
	ffusco@...hat.com
Subject: Re: [PATCH net-next] virtio_net: migrate mergeable rx buffers to
 page frag allocators

On Mon, Oct 28, 2013 at 11:57:21PM -0400, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Mon, 28 Oct 2013 16:19:49 -0700
> 
> > On Mon, 2013-10-28 at 15:44 -0700, Michael Dalton wrote:
> >> The virtio_net driver's mergeable receive buffer allocator
> >> uses 4KB packet buffers. For MTU-sized traffic, SKB truesize
> >> is > 4KB but only ~1500 bytes of the buffer is used to store
> >> packet data, reducing the effective TCP window size
> >> substantially. This patch addresses the performance concerns
> >> with mergeable receive buffers by allocating MTU-sized packet
> >> buffers using page frag allocators. If more than MAX_SKB_FRAGS
> >> buffers are needed, the SKB frag_list is used.
> >> 
> >> Signed-off-by: Michael Dalton <mwdalton@...gle.com>
> >> ---
> > 
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > 
> > Daniel & Francesco, this should address the performance problem you
> > tried to address with ("tcp: rcvbuf autotuning improvements") 
> > 
> > ( http://www.spinics.net/lists/netdev/msg252642.html )
> 
> Applied, thanks everyone.

Hmm that was very quick. It *should* fix a bug, great.
But how about we wait for some Tested-by reports that it actually does?

-- 
MST
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