linux-kernel - Re: spinlocks -- why are releases inlined and acquires are not?

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Message-ID: <20080401083359.GB32272@elte.hu>
Date:	Tue, 1 Apr 2008 10:33:59 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: spinlocks -- why are releases inlined and acquires are not?

* Jiri Kosina <jkosina@...e.cz> wrote:

> > What is the reason for this asymetry? Shouldn't the acquiring 
> > functions be implemented in the very same way? Or at least, 
> > shouldn't all the __lockfunc functions be inlined?
> 
> i.e. is there any particular reason why we don't have something like 
> the patch below (implemented for all the lock variants of course, this 
> is just to demonstrate what I mean)?

IIRC the main reason we decided to uninline them was image size. So i'd 
suggest for you to check how this change impacts vmlinux size (on both 
64-bit and 32-bit), a typical distro config (or allyesconfig with lock 
debugging disabled).

If you do the test on x86.git/latest you'll also have the 
CONFIG_OPTIMIZE_INLINING=y and CONFIG_CC_OPTIMIZE_FOR_SIZE=y combination 
as well, which generates the most compact x86 kernel image ever.

	Ingo
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