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

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Date:	Tue, 4 Aug 2009 13:53:15 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	penberg@...helsinki.fi, a.p.zijlstra@...llo.nl, fweisbec@...il.com,
	rostedt@...dmis.org, mel@....ul.ie, lwoodman@...hat.com,
	riel@...hat.com, 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 Tue, 4 Aug 2009 22:35:26 +0200
Ingo Molnar <mingo@...e.hu> wrote:

> Did you never want to see whether firefox is leaking [any sort of] 
> memory, and if yes, on what callsites? Try something like on an 
> already running firefox context:
> 
>   perf stat -e kmem:mm_page_alloc \
>             -e kmem:mm_pagevec_free \
>             -e kmem:mm_page_free_direct \
>      -p $(pidof firefox-bin) sleep 10
> 
> ... and "perf record" for the specific callsites.

OK, that would be useful.  What does the output look like?

In what way is it superior to existing ways of finding leaks?

> this perf stuff is immensely flexible and a very unixish 
> abstraction. The perf.data contains timestamped trace entries of 
> page allocations and freeing done.
> 
> [...]
> > It would be nice to at least partially remove the vmstat/meminfo 
> > infrastructure but I don't think we can do that?
> 
> at least meminfo is an ABI for sure - vmstat too really.
> 
> But we can stop adding new fields into obsolete, inflexible and 
> clearly deficient interfaces, and we can standardize new 
> instrumentation to use modern instrumentation facilities - i.e. 
> tracepoints and perfcounters.

That's bad.  Is there really no way in which we can consolidate _any_
of that infrastructure?  We just pile in new stuff alongside the old?

The worst part is needing two unrelated sets of userspace tools to
access basically-identical things.


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