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Date: Mon, 28 Apr 2008 09:54:37 -0700 (PDT)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Thomas Gleixner <tglx@linutronix.de>
cc: Harvey Harrison <harvey.harrison@gmail.com>, Ingo Molnar <mingo@elte.hu>,
       Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>, David Miller <davem@davemloft.net>
Subject: Re: [PATCH] bitops: simplify generic bit finding functions
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On Mon, 28 Apr 2008, Thomas Gleixner wrote:

> On Mon, 28 Apr 2008, Linus Torvalds wrote:
> > >
> > > How about making the optimization controlled by a config switch so
> > > arch maintainers can decide whether they want to enable the constant
> > > optimization or unconditionally call the lib function ?
> > 
> > No.
> > 
> > This is just making that damn header line look worse and worse.
> > 
> > Is there a _reason_ to optimize this stupid function this way?
> 
> On architectures which have a find bit instruction we can replace the
> call to the library function by a single instruction when the size of
> the bitmap is less/equal bits per long and when the bitnr is a
> constant.

That's not what I asked.

I asked whether there is a *reason* to optimize this and cause all these 
stupid problems.

Is there a real hot path anywhere that actually uses this and depends on 
it?

		Linus