Date: Fri, 23 Dec 2005 11:22:03 -0800 (PST)
From: Zwane Mwaikambo <zwane@arm.linux.org.uk>
To: Eric Dumazet <dada1@cosmosbay.com>
cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
       Pekka Enberg <penberg@cs.helsinki.fi>,
       Christoph Lameter <christoph@lameter.com>,
       Alok N Kataria <alokk@calsoftinc.com>,
       Shobhit Dayal <shobhit@calsoftinc.com>,
       Shai Fultheim <shai@scalex86.org>, Matt Mackall <mpm@selenic.com>,
       Andrew Morton <akpm@osdl.org>, john stultz <johnstul@us.ibm.com>,
       Gunter Ohrner <G.Ohrner@post.rwth-aachen.de>,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH RT 00/02] SLOB optimizations
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On Thu, 22 Dec 2005, Eric Dumazet wrote:

> Ingo Molnar a =E9crit :
> >=20
> > CLI/STI is extremely fast. (In fact in the -rt tree i'm using them with=
in
> > mutexes instead of preempt_enable()/preempt_disable(), because they are
> > faster and generate less register side-effect.)
> >=20
>=20
> Yes, but most of my machines have a ! CONFIG_PREEMPT kernel, so
> preempt_enable()/preempt_disable() are empty, thus faster than CLI/STI fo=
r
> sure :)
>=20
> Then, maybe the patch that moves 'current' in a dedicated x86_64 register=
 may
> help to lower  the cost of preempt_enable()/preempt_disable() on a
> CONFIG_PREEMPT kernel ?

I'm not sure if it'll make much of a difference over;

mov    %gs:offset,%reg

So 'current' already is fairly fast on x86_64.
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