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

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Message-ID: <1383002389.4344.7.camel@edumazet-glaptop.roam.corp.google.com>
Date:	Mon, 28 Oct 2013 16:19:49 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Michael Dalton <mwdalton@...gle.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	virtualization@...ts.linux-foundation.org,
	Francesco Fusco <ffusco@...hat.com>
Subject: Re: [PATCH net-next] virtio_net: migrate mergeable rx buffers to
 page frag allocators

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 )

Thanks !


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