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From: "Alexander van Heukelum" <heukelum@fastmail.fm>
To: "Linus Torvalds" <torvalds@linux-foundation.org>,
	"Harvey Harrison" <harvey.harrison@gmail.com>,
	"David S. Miller" <davem@davemloft.net>
Cc: "Ingo Molnar" <mingo@elte.hu>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"LKML" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] bitops: simplify generic bit finding functions
Date: Mon, 28 Apr 2008 16:58:43 +0200	[thread overview]
Message-ID: <1209394723.22937.1250267923@webmail.messagingengine.com> (raw)
In-Reply-To: <alpine.LFD.1.10.0804271325350.3119@woody.linux-foundation.org>

On Sun, 27 Apr 2008 13:26:34 -0700 (PDT), "Linus Torvalds"
<torvalds@linux-foundation.org> said:
> On Sun, 27 Apr 2008, Harvey Harrison wrote:
> >
> > No need for a sentinal if we explicitly catch the no bits/all bits set
> > cases, make it clear they are special cases returning size/BITS_PER_LONG.
> 
> These things need to be re-done anyway. David already complained that the 
> thing inlines to something much much too big.
> 
> Let's just make it not be an inline at all.

Hello,

I think that's the wrong way to go about it. The problem that David
Miller pointed out was that the small-bitmap optimization caused an
inliningdisaster. Apparently, the generic version of __ffs is very
big on sparc64. In my opinion the implementation of __ffs should be
made out of line. If you move the wrapper of find_first_bit etc
out of line, all possibilities of optimization will be destroyed.
Better to remove them completely, then.

Greetings,
    Alexander

> 		Linus
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-- 
  Alexander van Heukelum
  heukelum@fastmail.fm

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  parent reply	other threads:[~2008-04-28 14:58 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-04-27 20:19 [PATCH] bitops: simplify generic bit finding functions Harvey Harrison
2008-04-27 20:26 ` Linus Torvalds
2008-04-27 20:29   ` Harvey Harrison
2008-04-27 20:36     ` Al Viro
2008-04-27 20:38       ` Harvey Harrison
2008-04-27 20:38     ` Linus Torvalds
2008-04-27 21:02       ` Al Viro
2008-04-28 14:04   ` Thomas Gleixner
2008-04-28 15:10     ` Alexander van Heukelum
2008-04-28 15:58       ` Thomas Gleixner
2008-04-28 16:25     ` Linus Torvalds
2008-04-28 16:47       ` Thomas Gleixner
2008-04-28 16:54         ` Linus Torvalds
2008-04-28 19:26           ` Thomas Gleixner
2008-04-28 19:37             ` Linus Torvalds
2008-04-28 21:55               ` Ingo Molnar
2008-04-29 10:01               ` [PATCH] bitops: remove "optimizations" Thomas Gleixner
2008-04-29 10:03                 ` David Miller
2008-04-29 12:34                   ` David Miller
2008-04-29 14:20                     ` Ingo Molnar
2008-04-29 22:31                       ` David Miller
2008-04-29 16:51                     ` Thomas Gleixner
2008-04-29 22:58                       ` David Miller
2008-04-29 23:30                         ` David Miller
2008-04-28 19:57           ` [PATCH] bitops: simplify generic bit finding functions Andi Kleen
2008-04-28 14:58   ` Alexander van Heukelum [this message]
2008-04-28 14:32 ` Alexander van Heukelum

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