linux-kernel - Re: [PATCH] lib/int_sqrt.c: Optimize square root function

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Message-ID: <1422939437.2293.6.camel@stgolabs.net>
Date:	Mon, 02 Feb 2015 20:57:17 -0800
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Anshul Garg <aksgarg1989@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	anshul.g@...sung.com
Subject: Re: [PATCH] lib/int_sqrt.c: Optimize square root function

On Mon, 2015-02-02 at 20:41 -0800, Davidlohr Bueso wrote:
> On Mon, 2015-02-02 at 11:13 -0800, Linus Torvalds wrote:
> > IOW, instead of
> > 
> >   m = 1UL << (BITS_PER_LONG - 2);
> > 
> > perhaps something like
> > 
> >    m = 1UL << (BITS_PER_LONG/2- 2);
> >    if (m < x)
> >        m <<= BITS_PER_LONG/2;

Assuming small values mostly, we could also try more aggressive
estimators for BITS_PER_LONG == 64. But then again, it probably doesn't
matter.

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