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

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Message-ID: <20140507172924.GE3694@arm.com>
Date:	Wed, 7 May 2014 18:29:24 +0100
From:	Will Deacon <will.deacon@....com>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	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

Hi Vince,

On Mon, Feb 24, 2014 at 03:37:11PM +0000, Vince Weaver wrote:
> On Mon, 24 Feb 2014, Will Deacon wrote:
> > On Fri, Jan 17, 2014 at 05:45:04AM +0000, Vince Weaver wrote:
> > > On Thu, 16 Jan 2014, Peter Zijlstra wrote:
> > > 
> > > > Yeah I suppose we could do something like that. Maybe something like:
> > > > 
> > > > # cat /sys/bus/event_source/devices/cpu/flags
> > > > int precise filter
> > > 
> > > wouldn't that violate the "one value per file" rule?
> > > 
> > > I guess we could also stick it in the mmap page somewhere, as tools like 
> > > PAPI already have to check there for things like rdpmc support.
> > > 
> > > 
> > > Anyway, here's a first pass at a generic fix for this issue.  I'm sure the 
> > > code is pretty horrible, I don't usually mess with the perf code at this 
> > > level.  I haven't tested yet as it touched enough files that the rasp-pi 
> > > is going to take a few hours to finish compiling.
> > > 
> > > Am I on the right track, or totally off here?
> > 
> > Where did we get to with this? If the generic changes are going to take some
> > time, I'm happy to take a temporary (non-invasive) fix in the ARM backend while
> > you sort out the core.
> 
> OK, let me revisit the patches.  The last set of generic ones I sent out 
> actually was broken on ARM and I've been meaning to straighten things out 
> and send a proper follow up patch set but got distracted by other perf 
> related issues.

Any luck with this? I just got (another) report of a PMU with borked
interrupts, so a fix would be great if you've got one.

Will
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