Subject: Re: [Patch] mm tracepoints
From: Larry Woodman <lwoodman@redhat.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>, Nick Piggin <npiggin@suse.de>,
       Steven Rostedt <rostedt@goodmis.org>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       linux-kernel@vger.kernel.org, peterz@infradead.org, fweisbec@gmail.com,
       Peter Zijlstra <a.p.zijlstra@chello.nl>
In-Reply-To: <20090306171016.GA32128@elte.hu>
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Date: Fri, 06 Mar 2009 14:22:00 -0500
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On Fri, 2009-03-06 at 18:10 +0100, Ingo Molnar wrote:
> * Larry Woodman <lwoodman@redhat.com> wrote:
> 
> > > Would that be useless or controversial? We know from 
> > > vma->mapping which inode it maps to. Knowing which file is 
> > > faulting in can be useful - especially when addresses are a 
> > > moving target such as under PIE or with dlopen(), etc.
> > > 
> > > 	Ingo
> > 
> > Attached is the updated patch that applies and builds 
> > correctly (sorry I missed the lockdep tracepoints that were 
> > added at the last minute). [...]
> 
> Looks pretty good and useful to me. I've Cc:-ed more mm folks, 
> it would be nice to hear their opinion about these tracepoints.
> 
> Andrew, Nick, Peter, what do you think?
> 
> About the motivation of these tracepoints: i suspect these 
> tracepoints reflect your years-long experience in dealing with 
> various MM regressions in the enterprise space and these 
> tracepoints would help understand such regressions 
> faster/easier?

Exactly, and without running some "debug enhanced kernel".

> 
> > [...]  As far as the filename:offset is concerned I am working 
> > on that.  Its not as simple as it looks because we have to 
> > follow a variable list of structs that can be null terminated 
> > several places along the way.
> 
> It's definitely not simple! I dont think it should be in this 
> base patch at all - it should be an add-on.
> 
> 	Ingo

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