linux-kernel - Re: [perf] Finding uninstalled modules Was Re: mailing list for trace users

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Date:	Wed, 23 Sep 2009 11:15:49 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Avi Kivity <avi@...hat.com>
Cc:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Mike Galbraith <efault@....de>, rostedt@...dmis.org,
	LKML <linux-kernel@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <mhiramat@...hat.com>
Subject: Re: [perf] Finding uninstalled modules Was Re: mailing list for
	trace users


* Avi Kivity <avi@...hat.com> wrote:

> On 09/22/2009 11:17 PM, Arnaldo Carvalho de Melo wrote:
>>
>>> $ perf annotate -v -v -k ~avi/kvm/linux-2.6/vmlinux -m vmx_vcpu_run  |
>>>      
>> Here is the problem, he is passing a vmlinux, that way we don't parse
>> /proc/kallsyms, so no module symbols, he uses -m to load the modules
>> symbols but mod_dso__load_module_paths only looks at /lib/modules/, i.e.
>> installed modules.
>>
>> I guess Avi hasn't installed modules, right? So the right fix for 
>> this case is to figure out where modules are from the path given to 
>> -k, i.e. we first use ~avi/kvm/linux-2.6/ as the modules path prefix 
>> and then fallback to /lib/modules if we can't find modules there, 
>> right?
>
> Modules were installed (I always load them with modprobe).  It's 
> possible that the installed modules were a later version than the 
> loaded modules, but Mike's reply leads me to believe there was a real 
> bug there.

Yes, definitely - 'perf annotate' not giving you what you expected is a 
bug by definition - regardless of how you build your kernel, how you 
loaded your modules and how the symbols and tables are distributed 
across the system.

	Ingo
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