linux-kernel - Re: [tip:perf/urgent] perf/x86: Enable raw event access to Intel offcore events

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Message-ID: <CABPqkBRHW0ZmeqADptvBySLZpi6jc_bEFKoukkA6rtd5o04ziQ@mail.gmail.com>
Date:	Mon, 21 Nov 2011 20:04:02 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Vince Weaver <vweaver1@...s.utk.edu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>, mingo@...hat.com,
	hpa@...or.com, linux-kernel@...r.kernel.org, tglx@...utronix.de,
	mingo@...e.hu
Subject: Re: [tip:perf/urgent] perf/x86: Enable raw event access to Intel
 offcore events

Vince,

On Mon, Nov 21, 2011 at 8:01 PM, Vince Weaver <vweaver1@...s.utk.edu> wrote:
> On Mon, 21 Nov 2011, Peter Zijlstra wrote:
>> On Mon, 2011-11-21 at 13:24 -0500, Vince Weaver wrote:
>
>> > Now I'll have to find something else
>> > to complain about, probably the scedulability issue introduced with the
>> > NMI watchdog.
>>
>> But you can disable that thing, right?
>>
>> echo 0 > /proc/sys/kernel/nmi_watchdog;
>>
>> or so should do the trick.
>
> yes, if the user running PAPI has root.
>
> That's unfortunately not always the case, and sometimes people want to
> have both the NMI watchdog operating and use PAPI simultaneously.
>

I don't understand why you have a problem with NMI watchdog. Multiplexing
allows you to still measure more events than there are counters.

> We have a workaround, but it currently disables kernel multiplexing and a
> few other nice features.
>
> Vince
> vweaver1@...s.utk.edu
>
>
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