linux-kernel - Re: [patch/rfc] perf on raspberry-pi without overflow interrupt

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Date:	Thu, 16 Jan 2014 12:13:10 -0500 (EST)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	Will Deacon <will.deacon@....com>,
	Chad Paradis <chad.paradis@...t.maine.edu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Stephane Eranian <eranian@...il.com>
Subject: Re: [patch/rfc] perf on raspberry-pi without overflow interrupt

On Tue, 14 Jan 2014, Peter Zijlstra wrote:

> On Mon, Jan 13, 2014 at 11:55:17PM -0500, Vince Weaver wrote:

> > I don't see an existing pmu capabilities struct... or do you mean
> > coming up with one?
> 
> Yeah, adding one.

So would it be a struct, or just an integer with flags?

> > Would it only hold an "overflow_interrupt_available" flag, or are
> > there other generic capabilities it would be handy to know about?
> 
> Possible (other) flags could be:
> 
>   PMU_HAS_INT      -- would allow sampling events
>   PMU_HAS_PRECISE  -- would allow any ::precise value
>   PMU_HAS_FILTER   -- would allow all os/user/etc. flags

should we export these to userspace somehow?

It would be handy to be able to tell you're getting EOPNOTSUP because
PMU_HAS_INT is not set for your pmu, rather than trying to guess why 
things are failing.

Vince
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