netdev - Re: [PATCH net-net] net: loopback: set default mtu to 64K

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Message-ID: <1348518796.26828.1651.camel@edumazet-glaptop>
Date:	Mon, 24 Sep 2012 22:33:16 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...hat.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-net] net: loopback: set default mtu to 64K

On Mon, 2012-09-24 at 16:24 -0400, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Mon, 24 Sep 2012 10:28:59 +0200
> 
> > From: Eric Dumazet <edumazet@...gle.com>
> > 
> > loopback current mtu of 16436 bytes allows no more than 3 MSS TCP
> > segments per frame, or 48 Kbytes. Changing mtu to 64K allows TCP
> > stack to build large frames and significantly reduces stack overhead.
> > 
> > Performance boost on bulk TCP transferts can be up to 30 %, partly
> > because we now have one ACK message for two 64KB segments, and a lower
> > probability of hitting /proc/sys/net/ipv4/tcp_reordering default limit.
> > 
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> 
> This gives a nice %13 improvement on my SPARC-T4 box as well.
> 
> Applied, thanks Eric.

the biggest increase is with

netperf -- -m 63K

I reach 50000 Mbytes/second


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