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To: Andi Kleen <andi@firstfloor.org>
Cc: Joerg Roedel <joro@8bytes.org>, Ingo Molnar <mingo@elte.hu>,
       "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
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       Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: Re: [PATCH] Enhance perf to collect KVM guest os statistics from host side
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From: Soeren Sandmann <sandmann@daimi.au.dk>
Date: 23 Mar 2010 15:04:57 +0100
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Andi Kleen <andi@firstfloor.org> writes:

> Soeren Sandmann <sandmann@daimi.au.dk> writes:
> >
> > To fix that problem, it seems like we need some way to have python
> > export what is going on. Maybe the same mechanism could be used to
> > both access what is going on in qemu and python.
> 
> oprofile already has an interface to let JITs export
> information about the JITed code. C Python is not a JIT,
> but presumably one of the python JITs could do it.
> 
> http://oprofile.sourceforge.net/doc/devel/index.html

It's not that I personally want to profile a particular python
program. I'm interested in the more general problem of extracting more
information from profiled user space programs than just stack traces.

Examples:

        - What is going on inside QEMU? 

        - Which client is the X server servicing?

        - What parts of a python/shell/scheme/javascript program is
          taking the most CPU time?

I don't think the oprofile JIT interface solves any of these
problems. (In fact, I don't see why the JIT problem is even hard. The
JIT compiler can just generate a little ELF file with symbols in it,
and the profiler can pick it up through the mmap events that you get
through the perf interface).

> I know it's not envogue anymore and you won't be a approved 
> cool kid if you do, but you could just use oprofile? 

I am bringing this up because I want to extend sysprof to be more
useful. 


Soren