linux-kernel - Re: [PATCH] Optimize int_sqrt for small values for faster idle

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Message-ID: <20160128224011.GL31686@two.firstfloor.org>
Date:	Thu, 28 Jan 2016 23:40:11 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, davidlohr.bueso@...com,
	rafael.j.wysocki@...el.com, lenb@...nel.org,
	Andi Kleen <ak@...ux.intel.com>,
	"anshul.g" <anshul.g@...sung.com>
Subject: Re: [PATCH] Optimize int_sqrt for small values for faster idle

> This thread might be relevant:
> 
> https://lkml.org/lkml/2015/2/2/600
> 
> and perhaps using fls might still be a good approach.

Linus wrote:


>>>
We *probably* have some argument range that we care more about, which
is why I'd like to know what the profile is that triggered this
optimization, and what the common argument range is.
<<<

That's exactly what I did. Used perf probe to get the common
range and optimize for that.

-Andi