linux-kernel - Re: [PATCH] Reduce the number of expensive division instructions done by _parse

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Message-ID: <26494.1328815383@redhat.com>
Date:	Thu, 09 Feb 2012 19:23:03 +0000
From:	David Howells <dhowells@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	dhowells@...hat.com, Eric Dumazet <eric.dumazet@...il.com>,
	adobriyan@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Reduce the number of expensive division instructions done by _parse_integer()

Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> Btw, what was the load that you noticed this on?
> 
> Because quite frankly, I think we only support bases 8/10/16 in the
> kernel, and if you really have some case where this all is expensive,
> it might be better to simply have three different functions for the
> three bases. That would turn the multiplies into constants too, and
> also simplify the character tests.
> 
> That said, I can't really see how this could ever be all that hot a
> function. Did you ever see it in a profile, or was this all just from
> looking at the code?

Just by looking at the code.  I can't think of anything particularly where
this is likely to be encountered in a critical path.

David
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