linux-kernel - Re: [PATCH] [3/5] Mark complex bitops.h inlines as __always

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Message-ID: <20090107131846.GF3529@elte.hu>
Date:	Wed, 7 Jan 2009 14:18:46 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [3/5] Mark complex bitops.h inlines as __always_inline


* Hugh Dickins <hugh@...itas.com> wrote:

> Hugh Dickins noticed that released gcc versions building the kernel with 
> CONFIG_OPTIMIZE_INLINING=y don't inline some of the bitops - sometimes 
> generating very inefficient pageflag tests, and many instances of 
> constant_test_bit().

Could you quantify that please?

We really dont want to reintroduce __always_inline just for performance / 
code size reasons. If GCC messes up and makes a larger / more inefficient 
kernel, GCC will be fixed. CONFIG_OPTIMIZE_INLINING is default-off, so 
enable it only if it improves your kernel.

	Ingo
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