linux-kernel - Re: [PATCH] modules: Take a shortcut for checking if an address is in a module

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Message-ID: <19f34abd0806111154q77739a2m8dcff24e2f9a3922@mail.gmail.com>
Date:	Wed, 11 Jun 2008 20:54:46 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Arjan van de Ven" <arjan@...radead.org>
Cc:	"Rusty Russell" <rusty@...tcorp.com.au>, mingo@...e.hu,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] modules: Take a shortcut for checking if an address is in a module

On 6/11/08, Arjan van de Ven <arjan@...radead.org> wrote:
> On Wed, 11 Jun 2008 21:12:08 +1000
>  Rusty Russell <rusty@...tcorp.com.au> wrote:
>
>  > On Wednesday 11 June 2008 06:05:19 Arjan van de Ven wrote:
>  > > From: Arjan van de Ven <arjan@...ux.intel.com>
>  > > Subject: [PATCH] modules: Take a shortcut for checking if an
>  > > address is in a module
>  > >
>  > > Various pieces of the kernel (lockdep, latencytop, etc) tend to
>  > > store backtraces, sometimes at a relatively high frequency. In
>  > > itself this isn't a big performance deal (after all you're using
>  > > diagnostics features), but there have been some complaints from
>  > > people who have over 100 modules loaded that this is a tad too slow.

Would it be overkill to simply drop the module addresses in an rbtree
and use that instead of a linear search over all the modules?

It would probably take a fair number of lines in C, and with a little
memory overhead, but the speed-up should be great. Should I give it a
try? (It would be arch-independent too.)


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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