linux-kernel - Re: [PATCH 07/13] perf evlist: Fix creation of cpu map

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Date:	Fri, 27 Apr 2012 09:16:18 +0900
From:	Namhyung Kim <namhyung.kim@....com>
To:	David Ahern <dsahern@...il.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/13] perf evlist: Fix creation of cpu map

Hi,

On Thu, 26 Apr 2012 15:22:55 -0600, David Ahern wrote:
> On 4/26/12 3:12 PM, Namhyung Kim wrote:
>> Hmm.. No, I can reproduce it without any of this series. And now I think
>> that it is not related to the number of cpus. On my 4 core (no
>> hyperthreading) machine at home, the result was same.
>>
>> BTW, did you change sysctl settings?
>>
>>    $ cat /sys/devices/system/cpu/online
>>    0-3
>>    $ grep . /proc/sys/kernel/perf_event_*
>>    /proc/sys/kernel/perf_event_max_sample_rate:100000
>>    /proc/sys/kernel/perf_event_mlock_kb:516
>>    /proc/sys/kernel/perf_event_paranoid:1
>
> $ grep . /proc/sys/kernel/perf_event_*
> /proc/sys/kernel/perf_event_max_sample_rate:100000
> /proc/sys/kernel/perf_event_mlock_kb:516
> /proc/sys/kernel/perf_event_paranoid:-1
>
> That last one is the key. I have it set to not paranoid and usually
> run perf a non-root user.
>

That's exactly what I want to see :). On perf_mmap() we have:

	if ((locked > lock_limit) && perf_paranoid_tracepoint_raw() &&
		!capable(CAP_IPC_LOCK)) {
		ret = -EPERM;
		goto unlock;
	}

So as long as you set perf_event_paranoid to -1 or run perf test as
root, you cannot see the failure.

Thanks,
Namhyung


>>    $ ./perf test 7
>>     7: Validate PERF_RECORD_* events&  perf_sample fields: FAILED!
>>    $ ./perf --version
>>    perf version 3.4.rc1
>
> running 3.4-rc4 kernel + perf from tip/perf/core branch.
>
> David
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