Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755299AbbESABB (ORCPT ); Mon, 18 May 2015 20:01:01 -0400 Received: from www.linutronix.de ([62.245.132.108]:51768 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755161AbbESAAo (ORCPT ); Mon, 18 May 2015 20:00:44 -0400 Message-Id: <20150518235150.080844281@linutronix.de> User-Agent: quilt/0.63-1 Date: Tue, 19 May 2015 00:00:55 -0000 From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , Vikas Shivappa , x86@kernel.org, Matt Fleming , Will Auld , Kanaka Juvva Subject: [patch 4/6] x86, perf, cqm: Avoid pointless msr write References: <20150518234114.574556332@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=x86-perf-cqm-avoid-pointless-msr-write.patch X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001,URIBL_BLOCKED=0.001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1062 Lines: 35 If the usage counter is non-zero there is no point to update the rmid in the PQR MSR. Signed-off-by: Thomas Gleixner --- arch/x86/kernel/cpu/perf_event_intel_cqm.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) Index: linux/arch/x86/kernel/cpu/perf_event_intel_cqm.c =================================================================== --- linux.orig/arch/x86/kernel/cpu/perf_event_intel_cqm.c +++ linux/arch/x86/kernel/cpu/perf_event_intel_cqm.c @@ -974,10 +974,12 @@ static void intel_cqm_event_start(struct event->hw.cqm_state &= ~PERF_HES_STOPPED; - if (state->cnt++) - WARN_ON_ONCE(state->rmid != rmid); - else + if (state->cnt++) { + if (!WARN_ON_ONCE(state->rmid != rmid)) + return; + } else { WARN_ON_ONCE(state->rmid); + } state->rmid = rmid; /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/