linux-kernel - Re: [PATCH 4/4] tracing, page-allocator: Add a postprocessing script for page-allocator-related ftrace events

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Message-ID: <20090806155451.GC6915@csn.ul.ie>
Date:	Thu, 6 Aug 2009 16:54:51 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Larry Woodman <lwoodman@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, mingo@...e.hu,
	peterz@...radead.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 4/4] tracing, page-allocator: Add a postprocessing
	script for page-allocator-related ftrace events

On Wed, Aug 05, 2009 at 10:53:50AM -0400, Larry Woodman wrote:
> On Tue, 2009-08-04 at 21:48 +0100, Mel Gorman wrote:
> 
> > > 
> > 
> > Adding and deleting tracepoints, rebuilding and rebooting the kernel is
> > obviously usable by developers but not a whole pile of use if
> > recompiling the kernel is not an option or you're trying to debug a
> > difficult-to-reproduce-but-is-happening-now type of problem.
> > 
> > Of the CC list, I believe Larry Woodman has the most experience with
> > these sort of problems in the field so I'm hoping he'll make some sort
> > of comment.
> > 
> 
> I am all for adding tracepoints that eliminate the need to locate a
> problem, add debug code, rebuild, reboot and retest until the real
> problem is found.  
> 
> Personally I have not seen as many problems in the page allocator as I
> have in the page reclaim code thats why the majority of my tracepoints
> were in vmscan.c 

I'd be surprised if you had, problems in page reclaim would be a lot
more obvious for a start. The page allocator happened to be where I wanted
tracepoints at the moment and I think the next patchset will act as a template
for how to introduce tracepoints which can be repeated for the reclaim points.

> However I do ACK this patch set because it provides
> the opportunity to zoom into the page allocator dynamically without
> needing to iterate through the cumbersome debug process.
> 

Thanks.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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