linux-kernel - Re: perf report for .ko files

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Date:	Tue, 26 Jan 2010 20:21:55 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	john smith <whalajam@...oo.com>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: perf report for .ko files

On Mon, 2010-01-25 at 16:34 -0800, john smith wrote:
> How can "perf report" be used to get info on (only) the specific manually loadable modules?
> Driver entry points are reported but without full breakdown (on all the calls).

Since its sampling it could be a function is just not hit, another
possibility is inlining of functions, we simply cannot see inlined
functions.

> If "--symbols" option is used, most of the symbols are not found.
> ("--dsos" doesn't seem to help)

I'm not a big module user, but I think --dsos should work, if not feel
free to send a patch to rectify this situation.

--dsos does appear to work on my laptop (where I have iwlagn as a module
since it sometimes needs a reload to start working, which is hard when
build in).

perf report --dsos "[iwlagn]"

does indeed give me all iwlagn hits, albeit without symbol information,
not sure why that is, /proc/kallsyms does seem to include some iwlagn
symbols.

Arnaldo might have a clue.

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