linux-kernel - Re: [PATCH] x86: Change x86 to use generic find_next

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Date:	09 Mar 2008 21:28:32 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Alexander van Heukelum <heukelum@...lshack.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>, heukelum@...tmail.fm
Subject: Re: [PATCH] x86: Change x86 to use generic find_next_bit

Alexander van Heukelum <heukelum@...lshack.com> writes:
> 
> If the bitmap size is not a multiple of BITS_PER_LONG, and no set 
> (cleared) bit is found, find_next_bit (find_next_zero_bit) returns a 
> value outside of the range [0,size]. The generic version always returns 
> exactly size.

With that change it is likely possible to remove the min(NR_CPUS in
lib/cpumask.c __first/__next_cpu. iirc it was just a workaround for
the x86 quirk. I suspect with such a change it would be possible to
inline those again, possibly speeding up some loops who do cpumask
walking (iirc the scheduler used to do that frequently)

-Andi

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