From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759726Ab2EIOgw (ORCPT ); Wed, 9 May 2012 10:36:52 -0400 Received: from terminus.zytor.com ([198.137.202.10]:41139 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758033Ab2EIOgv (ORCPT ); Wed, 9 May 2012 10:36:51 -0400 Date: Wed, 9 May 2012 07:36:32 -0700 From: tip-bot for Robert Richter Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, robert.richter@amd.com, a.p.zijlstra@chello.nl, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, robert.richter@amd.com, a.p.zijlstra@chello.nl, tglx@linutronix.de In-Reply-To: <1333390758-10893-10-git-send-email-robert.richter@amd.com> References: <1333390758-10893-10-git-send-email-robert.richter@amd.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf/x86-ibs: Extend hw period that triggers overflow Git-Commit-ID: 7caaf4d8241feecafb87919402b0a6dbb1b71d9e X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.6 (terminus.zytor.com [127.0.0.1]); Wed, 09 May 2012 07:36:38 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 7caaf4d8241feecafb87919402b0a6dbb1b71d9e Gitweb: http://git.kernel.org/tip/7caaf4d8241feecafb87919402b0a6dbb1b71d9e Author: Robert Richter AuthorDate: Mon, 2 Apr 2012 20:19:15 +0200 Committer: Ingo Molnar CommitDate: Wed, 9 May 2012 15:23:15 +0200 perf/x86-ibs: Extend hw period that triggers overflow If the last hw period is too short we might hit the irq handler which biases the results. Thus try to have a max last period that triggers the sw overflow. Signed-off-by: Robert Richter Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1333390758-10893-10-git-send-email-robert.richter@amd.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_amd_ibs.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c index 3e32908..cb51a3e 100644 --- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c +++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c @@ -85,8 +85,19 @@ perf_event_set_period(struct hw_perf_event *hwc, u64 min, u64 max, u64 *hw_perio overflow = 1; } - if (left > max) - left = max; + /* + * If the hw period that triggers the sw overflow is too short + * we might hit the irq handler. This biases the results. + * Thus we shorten the next-to-last period and set the last + * period to the max period. + */ + if (left > max) { + left -= max; + if (left > max) + left = max; + else if (left < min) + left = min; + } *hw_period = (u64)left;