linux-kernel - Re: [Patch] mm tracepoints update

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Date:	Wed, 22 Apr 2009 08:07:17 -0400
From:	Larry Woodman <lwoodman@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	eduard.munteanu@...ux360.ro, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, riel@...hat.com, rostedt@...dmis.org
Subject: Re: [Patch] mm tracepoints update

On Wed, 2009-04-22 at 11:57 +0200, Ingo Molnar wrote:
> * KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
> 
> > > I've cleaned up the mm tracepoints to track page allocation and 
> > > freeing, various types of pagefaults and unmaps, and critical 
> > > page reclamation routines.  This is useful for debugging memory 
> > > allocation issues and system performance problems under heavy 
> > > memory loads.
> > 
> > In past thread, Andrew pointed out bare page tracer isn't useful. 
> 
> (do you have a link to that mail?)
> 
> > Can you make good consumer?

I will work up some good examples of what these are useful for.  I use
the mm tracepoint data in the debugfs trace buffer to locate customer
performance problems associated with memory allocation, deallocation,
paging and swapping frequently, especially on large systems.

Larry

> 
> These MM tracepoints would be automatically seen by the 
> ftrace-analyzer GUI tool for example:
> 
>   git://git.kernel.org/pub/scm/utils/kernel/ftrace/ftrace.git
> 
> And could also be seen by other tools such as kmemtrace. Beyond, of 
> course, embedding in function tracer output.
> 
> Here's the list of advantages of the types of tracepoints Larry is 
> proposing:
> 
>   - zero-copy and per-cpu splice() based tracing
>   - binary tracing without printf overhead
>   - structured logging records exposed under /debug/tracing/events
>   - trace events embedded in function tracer output and other plugins
>   - user-defined, per tracepoint filter expressions
> 
> I think the main review question is: are they properly structured 
> and do they expose essential information to analyze behavioral 
> details of the kernel in this area?
> 
> 	Ingo
> 
> --
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