linux-kernel - Re: [PATCH 0/5] x86 cleanup: convert round

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Date:	Tue, 29 Jul 2008 09:16:59 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Joerg Roedel <joerg.roedel@....com>, mingo@...hat.com,
	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 0/5] x86 cleanup: convert round_up() to roundup()


* Yinghai Lu <yhlu.kernel@...il.com> wrote:

> On Sat, Jul 26, 2008 at 6:39 AM, Ingo Molnar <mingo@...e.hu> wrote:
> >
> > * Joerg Roedel <joerg.roedel@....com> wrote:
> >
> >> The x86 architecture declares its own round_up macro. But there is a
> >> generic one in <linux/kernel.h> which can also be used. This patchset
> >> replaces the x86 round_up() macro with the generic roundup() one where
> >> possible. The patches have been compile-tested for 32 and 64 bit and
> >> boot-tested for 64 bit. If we can fix the other places too we can get
> >> rid of the x86 specific round_up() in the future.
> >
> > applied to tip/x86/cleanups - thanks Joerg!
> >
> these patches looks like some backward, aka wrong direction.
> 
> #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
> 
> #define round_up(x, y) (((x) + (y) - 1) & ~((y) - 1))
> #define round_down(x, y) ((x) & ~((y) - 1))
> 
> round_up looks more efficient.

hm, does it ever make a difference to the compiled output?

	Ingo
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