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From: Andi Kleen <andi@firstfloor.org>
To: Alexander van Heukelum <heukelum@mailshack.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
	"H. Peter Anvin" <hpa@zytor.com>,
	LKML <linux-kernel@vger.kernel.org>,
	heukelum@fastmail.fm
Subject: Re: [PATCH] x86: Change x86 to use generic find_next_bit
Date: 09 Mar 2008 21:28:32 +0100	[thread overview]
Message-ID: <87zlt7zlov.fsf@basil.nowhere.org> (raw)
In-Reply-To: <20080309200103.GA895@mailshack.com>

Alexander van Heukelum <heukelum@mailshack.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


  parent reply	other threads:[~2008-03-09 20:28 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-09 20:01 Alexander van Heukelum
2008-03-09 20:10 ` Ingo Molnar
2008-03-09 21:03   ` Andi Kleen
2008-03-09 21:32     ` Andi Kleen
2008-03-09 21:13   ` Alexander van Heukelum
2008-03-10  6:29     ` Ingo Molnar
2008-03-09 20:11 ` Ingo Molnar
2008-03-09 20:31   ` Alexander van Heukelum
2008-03-09 20:51     ` Ingo Molnar
2008-03-09 21:29       ` Andi Kleen
2008-03-10 23:17       ` [RFC/PATCH] x86: Optimize find_next_(zero_)bit for small constant-size bitmaps Alexander van Heukelum
2008-03-11  9:56         ` Ingo Molnar
2008-03-11 15:17           ` [PATCH] " Alexander van Heukelum
2008-03-11 15:22             ` [RFC] non-x86: " Alexander van Heukelum
2008-03-11 15:23             ` [PATCH] x86: " Ingo Molnar
2008-03-09 20:28 ` Andi Kleen [this message]
2008-03-09 21:31 ` [PATCH] x86: Change x86 to use generic find_next_bit Andi Kleen
2008-03-13 12:44 ` Aneesh Kumar K.V
2008-03-13 14:27   ` Alexander van Heukelum

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