From: Peter Zijlstra <peterz@infradead.org>
To: Lin Ming <ming.m.lin@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Matt Fleming <matt@console-pimps.org>,
Zhang Rui <rui.zhang@intel.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
lkml <linux-kernel@vger.kernel.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: Re: [RFC PATCH 2/2] perf stat: Use event group to simulate PMI on PMI-less hardware counter
Date: Wed, 10 Nov 2010 13:21:49 +0100 [thread overview]
Message-ID: <1289391709.2191.102.camel@laptop> (raw)
In-Reply-To: <1289369725.2430.39.camel@minggr.sh.intel.com>
On Wed, 2010-11-10 at 14:15 +0800, Lin Ming wrote:
> Some hardware counters(for example, Intel RAPL) can't generate interrupt
> when overflow. So we need to simulate the interrupt to periodically
> record the counter values. Otherwise, the counter may overflow and the
> wrong value is read.
>
> This patch uses event group to simulate PMI as suggested by Peter
> Zijlstra, http://marc.info/?l=linux-kernel&m=128220854801819&w=2
>
> create_group_counters() will create a group with 2 events, one hrtimer
> based event as the group leader, and the other event to count. The
> hrtimer is fired periodically, so the sibling event can record its
> counter value periodically as well.
I'm terribly confused here....
- you introduce perf_event_attr:pmi_simulate, but then you never
implement it -- nor do we need it afaict.
- you use grouped counters for perf-stat, perf-stat doesn't use
sampling so I don't see a need to group events to simulate the PMI.
next prev parent reply other threads:[~2010-11-10 12:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-10 6:15 [RFC PATCH 2/2] perf stat: Use event group to simulate PMI on PMI-less hardware counter Lin Ming
2010-11-10 12:21 ` Peter Zijlstra [this message]
2010-11-10 14:45 ` Lin Ming
2010-11-10 14:53 ` Peter Zijlstra
2010-11-10 15:06 ` Lin Ming
2010-11-10 15:08 ` Peter Zijlstra
2010-11-10 15:17 ` Matt Fleming
2010-11-11 2:00 ` Zhang Rui
2010-11-11 12:46 ` Peter Zijlstra
2010-11-12 0:32 ` Zhang Rui
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