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From: Tim Schmielau <tim@physik3.uni-rostock.de>
To: Stephen Hemminger <shemminger@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] udivdi3: 64 bit divide
Date: Thu, 1 Mar 2007 02:29:19 +0100 (CET)	[thread overview]
Message-ID: <Pine.LNX.4.63.0703010220210.21277@gockel.physik3.uni-rostock.de> (raw)
In-Reply-To: <20070227122437.da27c3cd.akpm@linux-foundation.org>

On Tue, 27 Feb 2007, Andrew Morton wrote:
> > On Mon, 26 Feb 2007 17:35:17 -0800 Stephen Hemminger <shemminger@linux-foundation.org> wrote:
> > The kernel already has several implmentations and usages of 64 by 64 
> > bit divide.
> > 
> > Although it is significantly slower, there are places that need it so
> > provide one generic version using scaling, and allow existing platform
> > versions to continue.
> 
> The reason we implement 64/32 via do_div() is, for better or for worse, to
> make people think before they use it.  And to make it stand out, and so
> that we discover places that are using it by accident, where they could use
> something cheaper.

IMHO it is even more important that the user of your 64/64 div is aware 
that it only returns an approximate result.

I certainly don't want to have any code in the kernel that by accident 
makes an allocation a few bytes short of the actual size of the object 
(just to make up a drastic example).

Tim

      parent reply	other threads:[~2007-03-01  1:29 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-27  1:35 [PATCH] udivdi3: 64 bit divide Stephen Hemminger
2007-02-27 20:24 ` Andrew Morton
2007-02-27 21:18   ` Stephen Hemminger
2007-02-27 21:36     ` Andrew Morton
2007-02-27 22:24       ` Russell King
2007-02-27 22:39         ` Ian Molton
2007-02-28 22:30           ` Jan Engelhardt
2007-03-01 17:02             ` Ian Molton
2007-03-01  1:29   ` Tim Schmielau [this message]

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