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Date: Thu, 1 Jul 2010 16:31:12 +0100
From: MattFleming <matt@console-pimps.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>, paulus <paulus@samba.org>,
       stephane eranian <eranian@googlemail.com>,
       Robert Richter <robert.richter@amd.com>,
       Paul Mundt <lethal@linux-sh.org>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Cyrill Gorcunov <gorcunov@gmail.com>, Lin Ming <ming.m.lin@intel.com>,
       Yanmin <yanmin_zhang@linux.intel.com>,
       Deng-Cheng Zhu <dengcheng.zhu@gmail.com>,
       David Miller <davem@davemloft.net>, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 00/11] perf pmu interface -v2
Message-ID: <20100701153112.GA13511@console-pimps.org>
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On Thu, Jul 01, 2010 at 05:02:35PM +0200, Peter Zijlstra wrote:
> 
> Matt, you said it broke SH completely, but did you try perf stat? perf
> record is not supposed to work on SH due to the hardware not having an
> overflow interrupt.

perf record does work to some degree. It definitely worked before
applying your changes but not after. I admit I haven't really read the
perf event code, but Paul will know.

> Which made me think, what on SH guarantees we update the counter often
> enough not to suffer from counter wrap? Would it make sense to make the
> SH code hook into their arch tick handler and update the counters from
> there?

This was the way that the oprofile code used to work. Paul and I were
talking about using a hrtimer to sample performance counters as
opposed to piggy-backing on the tick handler.