linux-kernel - Re: find_new_bit bloat from x86 tree...

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Message-ID: <20080427204129.GB25300@elte.hu>
Date:	Sun, 27 Apr 2008 22:41:29 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	David Miller <davem@...emloft.net>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, viro@...IV.linux.org.uk,
	Alexander van Heukelum <heukelum@...lshack.com>
Subject: Re: find_new_bit bloat from x86 tree...


* David Miller <davem@...emloft.net> wrote:

> Ingo, what the heck is this?
> 
> commit 64970b68d2b3ed32b964b0b30b1b98518fde388e
> Author: Alexander van Heukelum <heukelum@...lshack.com>

(Alexander Cc:-ed.)

> Date:   Tue Mar 11 16:17:19 2008 +0100
> 
>     x86, generic: optimize find_next_(zero_)bit for small constant-size bitmaps
> 
> Thanks for bloating up the inline expansion of this thing on every 
> architecture that doesn't do __ffs() in a simple sequence of a few 
> instructions like x86 does.

ok, that's bad. How much is the before/after vmlinux btw, i guess you 
measured it? We could either make it per arch selectable, or we could 
just uninline it all. It shouldnt be a big deal on x86 and it should 
help on RISC platforms.

	Ingo
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