linux-kernel - Re: A question sort_main

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Message-ID: <20081120214717.1a02a9af@infradead.org>
Date:	Thu, 20 Nov 2008 21:47:17 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	"Peter Teoh" <htmldeveloper@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Sam Ravnborg" <sam@...nborg.org>
Subject: Re: A question sort_main_extable()

On Fri, 21 Nov 2008 13:42:56 +0800
"Peter Teoh" <htmldeveloper@...il.com> wrote:

> Inside start_kernel() there is a call to sort_main_extable().
> 
> void sort_extable(struct exception_table_entry *start,
>                  struct exception_table_entry *finish)
> {
>        sort(start, finish - start, sizeof(struct
> exception_table_entry), cmp_ex, NULL);
> }
> 
> With reference to
> http://tuxology.net/2008/07/08/benchmarking-boot-latency-on-x86/, I
> think it can help bootup latency (how much I got no number) if the
> sorting is done post-compilation time, instead of dynamically
> everytime the system bootup.  (perhaps at the stage of modposting,
> when all the vmlinux, kernel modules objects have been generated, so
> extracting out the exceptions strings is possible?)  Is this a
> possible optimization?

we used to do this but it was a pain and extremely fragile. Runtime
sorting makes it very robust at least.

The sort is really quick though; I've spent a lot of time on boot time
and this guy never showed up for me.



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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