linux-kernel - Re: [patch 0/4] perf_counter tools: support annotation of live kernel modules

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Message-Id: <1246519076.6384.22.camel@marge.simson.net>
Date:	Thu, 02 Jul 2009 09:17:56 +0200
From:	Mike Galbraith <efault@....de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [patch 0/4] perf_counter tools: support annotation of live
 kernel modules

On Thu, 2009-07-02 at 08:47 +0200, Ingo Molnar wrote:
> * Mike Galbraith <efault@....de> wrote:
> 
> > Per $subject, this patch set only supports for the LIVE kernel.  
> > It adds support infrastructure for path discovery, load address 
> > lookup, and symbol generation of live kernel modules.
> > 
> > TODO includes resurrection of live annotation in perf top, and 
> > support for annotation and report generation of other than live 
> > modules.  As the patch set sits, Perf top can generate symbols 
> > from live binaries, but there's no live annotation capability yet.
> > 
> > patch1: perf_counter tools: Make symbol loading consistently return number of loaded symbols.
> > patch2: perf_counter tools: Add infrastructure to support loading of kernel module symbols
> > patch3: perf_counter tools: connect module support infrastructure to symbol loading infrastructure
> > patch4: perf_counter tools: Enable kernel module symbol loading in tools
> > 
> > Comments and suggestions most welcome.
> 
> Looks very nice! I've applied it with a few minor stylistic fixlets 
> and a tad more verbose changelogs.

Thanks!

(sorry about changelogs, I did stare at them, nothing spiffy happened)

> I'm wondering about the next step: couldnt we somehow guess at the 
> position of the vmlinux too, validate somehow that it corresponds to 
> the kernel we are running - and then use it automatically and by 
> default?

I don't know of a way to discover where the image lives.  Been pondering
that very thing, along with idiot-proofing.

> Plus, offline analysis would be nice as well i suspect - being able 
> to look at profiles on a different box?

Yes, that's high on my TODO.  I've been pondering a perf archive tool
that would package everything that's needed to do analysis on a
different box.  One big problem though, is that while you can easily
package vmlinux and modules, what about all the userland binaries?  A
large perf.data and/or debug info binaries can easily make transport
impractical enough.

After I resurrect (well, try) live annotation in top, I'll fiddle with
offline kernel analysis.

	-Mike

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