From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: Loopback and Nagle's algorithm
Date: Tue, 12 Apr 2011 15:08:23 +0200
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Cc: Adam McLaurin <lkml@irotas.net>,
	Will Newton <will.newton@gmail.com>,
	linux-kernel@vger.kernel.org, netdev <netdev@vger.kernel.org>
To: Jiri Kosina <jkosina@suse.cz>
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Le mardi 12 avril 2011 =C3=A0 13:54 +0200, Jiri Kosina a =C3=A9crit :
> On Tue, 12 Apr 2011, Adam McLaurin wrote:
>=20
> > > It may be caused by an increase in context switch rate, as both s=
ender
> > > and receiver are on the same machine.
> >=20
> > I'm not sure that's what's happening, since the box where I'm runni=
ng
> > this test has 8 physical CPU's and 32 cores in total.
>=20
> Have you tried firing up the testcase under perf, to see what it reve=
als=20
> as the bottleneck?
>=20
CC netdev

This rings a bell here.

I suspect we hit mod_timer() / lock_timer_base()  because of delack
timer constantly changing.

I remember raising this point last year :

http://kerneltrap.org/mailarchive/linux-netdev/2010/5/20/6277741

David answer :=20
http://kerneltrap.org/mailarchive/linux-netdev/2010/6/2/6278430

I am afraid no change was done...