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

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 4 Aug 2009 22:35:26 +0200
Ingo Molnar <mingo@elte.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.