Date: Wed, 15 Sep 2004 17:58:36 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <ak@muc.de>
Cc: linux-kernel@vger.kernel.org, Lee Revell <rlrevell@joe-job.com>
Subject: Re: [patch] remove the BKL (Big Kernel Lock), this time for real
Message-ID: <20040915155836.GA11925@elte.hu>
References: <2EJTp-7bx-1@gated-at.bofh.it> <m3vfefa61l.fsf@averell.firstfloor.org>
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* Andi Kleen <ak@muc.de> wrote:

> Ingo Molnar <mingo@elte.hu> writes:
> 
> > the attached patch is a new approach to get rid of Linux's Big Kernel
> > Lock as we know it today.
> 
> Interesting approach. Did you measure what it does to context switch
> rates? Usually adding semaphores tends to increase them a lot.

not yet - i've coded it up today. Perhaps the lowlatency audio folks
(who are most interested in BKL-latency removal) could report some
numbers?

but as i've replied to Linus too, i believe that _if_ the context-switch
rate goes up then some piece of code uses the BKL way too often! So
having a semaphore here might in fact help fixing those rare cases.

> One minor comment only: 
> Please CSE "current" manually. It generates much better code
> on some architectures because the compiler cannot do it for you.

yeah, agreed, will do.

	Ingo
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