linux-kernel - Re: Need help with register_page_fault

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Message-ID: <20071118214200.526075a6@laptopd505.fenrus.org>
Date:	Sun, 18 Nov 2007 21:42:00 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Pavel Roskin <proski@....org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Need help with register_page_fault_notifier() replacement in
 2.6.24

On Mon, 19 Nov 2007 00:29:46 -0500
Pavel Roskin <proski@....org> wrote:

> Quoting Arjan van de Ven <arjan@...radead.org>:
> 
> > if it's just for a custom case (as it sounds like).. a simple small
> > change to the pagefault handler sounds like the easiest thing to
> > do... (eg just a direct function call to what would have been your
> > notifier)
> 
> Thanks!  Actually, the idea is to make it easy many people to run
> the trace without having them to patch or downgrade their kernels.
> Also, it would be convenient for ath5k developers to run (and
> perhaps improve) the trace on the current development kernel.
> 
> Also, the code was lifted from some nvidia debugging tool, so the  
> improved code could be contributed back there.
> 
> I guess if there is no simple answer, I'll have to try a few crazy  
> ideas.  If nothing works, the fault handler chain could be
> reinstated, perhaps as a separate configuration option.

a generic "IO trace"  function (as config
option) sounds actually like a good idea... that could do a direct call
if the config option is enabled (as well as some sysctl thing I
suspect, so that you can turn it on and off as you want)... I would
entirely support one of those going to mainline.

The problem with a chain is that those are quite expensive to run, and
page faults should really be a fast operation... so the normal case
should be a light as possible.

> 


-- 
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