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From: Peter Zijlstra <peterz@infradead.org>
To: torvalds@linux-foundation.org, akpm@linux-foundation.org
Cc: dave@stgolabs.net, aksgarg1989@gmail.com, tglx@linutronix.de,
	mingo@kernel.org, will.deacon@arm.com, joe@perches.com,
	peterz@infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 0/3] lib/int_sqrt: Fix, optimize and document
Date: Mon, 24 Jul 2017 17:16:30 +0200	[thread overview]
Message-ID: <20170724151630.447009076@infradead.org> (raw)

Hi,

Here are a few patches that should improve things lib/int_sqrt. As stated
elsewhere; I'm looking at using int_sqrt() to calculate the stdev on a normal
distribution and am expecting the input values to be smallish.

In any case, these optimizations should work fine for large numbers too. And
if you have a find-last-set or count-leading-zeros instruction they rock ;-)

I can post the tool used to generate the numbers or do a patch to add it to
tools/testing/ if people care. The cold numbers are fairly sensitive to code
layout (GCC version, random changes etc..), so I expect the branch predictor of
my SKL is only partially confused or there's other things at play. However the
general trend in the numbers seems fairly stable.

             reply	other threads:[~2017-07-24 15:38 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-24 15:16 Peter Zijlstra [this message]
2017-07-24 15:16 ` [PATCH 1/3] lib/int_sqrt: Optimize small argument Peter Zijlstra
2017-07-24 15:16 ` [PATCH 2/3] lib/int_sqrt: Optimize initial value compute Peter Zijlstra
2017-07-24 17:35   ` Linus Torvalds
2017-07-25  8:17     ` Peter Zijlstra
2017-07-25 15:43       ` Linus Torvalds
2017-07-25 16:08         ` Peter Zijlstra
2017-07-25 11:50   ` Will Deacon
2017-07-24 15:16 ` [PATCH 3/3] lib/int_sqrt: Adjust comments Peter Zijlstra
2017-07-24 15:42 ` [PATCH 0/3] lib/int_sqrt: Fix, optimize and document Joe Perches

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