netdev - Re: [RFC] tcp: use order-3 pages in tcp

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Date:	Wed, 19 Sep 2012 17:14:19 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC] tcp: use order-3 pages in tcp_sendmsg()

On Mon, 2012-09-17 at 13:07 -0400, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Mon, 17 Sep 2012 19:04:53 +0200
> 
> > On Mon, 2012-09-17 at 19:02 +0200, Eric Dumazet wrote:
> > 
> >> A driver already exports a dev->gso_max_size, dev->gso_max_segs, I guess
> >> it could export a dev->max_seg_order (default to 0)
> > 
> > Oh well, if we use a per thread order-3 page, a driver wont define an
> > order, but the max size of a segment (dev->max_seg_size).
> 
> Since you said that your audit showed that most can handle arbitrary
> segment sizes, it's better to default to infinity or similar.
> 
> Otherwise we'll have to annotate almost every single driver with a
> non-zero value, that's not an efficient way to handle this and
> deploy the higher performance quickly.

I did some tests and got no problem so far, even using splice() [ this
one was tricky because it only deals with order-0 pages at this moment ]

NIC tested : ixgbe, igb, bnx2x, tg3, mellanox mlx4

On loopback, performance of netperf goes from 31900 Mb/s to 38500 Mb/s,
thats a 20 % increase.



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