From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752791Ab1AQKqX (ORCPT ); Mon, 17 Jan 2011 05:46:23 -0500 Received: from hera.kernel.org ([140.211.167.34]:42746 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751090Ab1AQKqV (ORCPT ); Mon, 17 Jan 2011 05:46:21 -0500 Date: Mon, 17 Jan 2011 10:45:46 GMT From: tip-bot for Anton Blanchard Cc: linux-kernel@vger.kernel.org, paulus@samba.org, anton@samba.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, acme@ghostprotocols.net, benh@kernel.crashing.org, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, anton@samba.org, paulus@samba.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org, a.p.zijlstra@chello.nl, acme@ghostprotocols.net, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <20110117161742.5feb3761@kryten> References: <20110117161742.5feb3761@kryten> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] powerpc: perf: Fix frequency calculation for overflowing counters Message-ID: Git-Commit-ID: 4bca770ede796a1ef7af9c983166d5608d9ccfaf X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Mon, 17 Jan 2011 10:45:49 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 4bca770ede796a1ef7af9c983166d5608d9ccfaf Gitweb: http://git.kernel.org/tip/4bca770ede796a1ef7af9c983166d5608d9ccfaf Author: Anton Blanchard AuthorDate: Mon, 17 Jan 2011 16:17:42 +1100 Committer: Ingo Molnar CommitDate: Mon, 17 Jan 2011 11:43:02 +0100 powerpc: perf: Fix frequency calculation for overflowing counters When profiling a benchmark that is almost 100% userspace, I noticed some wildly inaccurate profiles that showed almost all time spent in the kernel. Closer examination shows we were programming a tiny number of cycles into the PMU after each overflow (about ~200 away from the next overflow). This gets us stuck in a loop which we eventually break out of by throttling the PMU (there are regular throttle/unthrottle events in the log). It looks like we aren't setting event->hw.last_period to something same and the frequency to period calculations in perf are going haywire. With the following patch we find the correct period after a few interrupts and stay there. I also see no more throttle events. Signed-off-by: Anton Blanchard Acked-by: Benjamin Herrenschmidt Cc: linuxppc-dev@lists.ozlabs.org Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo LKML-Reference: <20110117161742.5feb3761@kryten> Signed-off-by: Ingo Molnar --- arch/powerpc/kernel/perf_event.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/arch/powerpc/kernel/perf_event.c b/arch/powerpc/kernel/perf_event.c index 5674807..ab6f6be 100644 --- a/arch/powerpc/kernel/perf_event.c +++ b/arch/powerpc/kernel/perf_event.c @@ -1212,6 +1212,7 @@ static void record_and_restart(struct perf_event *event, unsigned long val, if (left <= 0) left = period; record = 1; + event->hw.last_period = event->hw.sample_period; } if (left < 0x80000000LL) val = 0x80000000LL - left;