linux-kernel - Re: [announce] "kill the Big Kernel Lock (BKL)" tree

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Date:	Thu, 15 May 2008 17:10:57 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	John Stoffel <john@...ffel.org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Alexander Viro <viro@....linux.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [announce] "kill the Big Kernel Lock (BKL)" tree

John Stoffel wrote:
>>>>>> "Andi" == Andi Kleen <andi@...stfloor.org> writes:
> 
> Andi> Linus Torvalds wrote:
>>> On Thu, 15 May 2008, Andi Kleen wrote:
>>>> The goal less being to get rid of BKL in old drivers, but not 
>>>> requiring BKL in new drivers. Basically all BKL assumptions
>>>> in interfaces really should go.
>>> No, we really do want to get rid of BKL in old drivers too. Or at least in 
>>> the interfaces.
> 
> Andi> In the interfaces definitely yes and all subsystems should have
> Andi> their own lock_kernel calls, but why in the old drivers? For
> Andi> those it's very unlikely they are used on any SMP system anyways
> Andi> (e.g. anything depending on CONFIG_ISA) or if they do only on 2
> Andi> CPU systems.
> 
> I'm still running an SMP server with ISA slots. 

I do too (although one CPU has died recently), but how many ISA devices
do you use in it? Mine used to have a ISA ISDN card, but that was it
and then no ISA anymore even though the slots are still in there.

Also on 2 CPU systems BKL is not that critical anyways. It only starts
to hurt on larger CPU counts.

-Andi

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