linux-kernel - Re: perf: regression -- missing /sys/devices/system/cpu/perf

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Message-ID: <4DDC1BB2.4090503@gmail.com>
Date:	Tue, 24 May 2011 14:57:22 -0600
From:	David Ahern <dsahern@...il.com>
To:	Vince Weaver <vweaver1@...s.utk.edu>
CC:	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org, paulus@...ba.org, acme@...hat.com
Subject: Re: perf: regression -- missing /sys/devices/system/cpu/perf_events



On 05/24/11 14:12, Vince Weaver wrote:
> On Tue, 24 May 2011, Ingo Molnar wrote:
>>
>> So, what is wrong with the method Peter suggested: the presence of the perf 
>> syscall (it not returning -ENOSYS) is bona fide evidence that perf is 
>> available.
> 
> it's just hard to do that from a shell script.

What about kallsyms:

grep sys_perf_event_open /proc/kallsyms

even with the new security feature you should be able to see that it
exists. The name has been the same since the counters->events rename in
cdd6c48. egrep for both names for kernels older than 2.6.31.

David


> 
> also, running the perf syscall can be tricky if you have a new kernel but 
> an older set of header files that doesn't have the syscall number defined.
> 
> Vince
> vweaver1@...s.utk.edu
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