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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
       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
From: Andi Kleen <andi@firstfloor.org>
References: <1209327591.14173.74.camel@brick>
	<alpine.LFD.1.10.0804271325350.3119@woody.linux-foundation.org>
	<alpine.LFD.1.10.0804281534530.3261@apollo.tec.linutronix.de>
	<alpine.LFD.1.10.0804280924270.3119@woody.linux-foundation.org>
	<alpine.LFD.1.10.0804281845250.3261@apollo.tec.linutronix.de>
	<alpine.LFD.1.10.0804280953570.3119@woody.linux-foundation.org>
Date: Mon, 28 Apr 2008 21:57:33 +0200
In-Reply-To: <alpine.LFD.1.10.0804280953570.3119@woody.linux-foundation.org> (Linus Torvalds's message of "Mon, 28 Apr 2008 09:54:37 -0700 (PDT)")
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Linus Torvalds <torvalds@linux-foundation.org> writes:
>
> Is there a real hot path anywhere that actually uses this and depends on 
> it?

A long time ago during profiling I found that in the scheduler back then
for_each_cpu() with find_next_bit() was somewhat hot. But I'm not sure it 
still would be in the new scheduler anyways and the test case a little
dumb anyways (overscheduling user space)

Still I think for_each_cpu() should be reasonably stream lined code.

-Andi