Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751758Ab2HMK2Q (ORCPT ); Mon, 13 Aug 2012 06:28:16 -0400 Received: from casper.infradead.org ([85.118.1.10]:36537 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751655Ab2HMK2N convert rfc822-to-8bit (ORCPT ); Mon, 13 Aug 2012 06:28:13 -0400 Message-ID: <1344853682.31459.20.camel@twins> Subject: Re: [BUG] perf: sharing of cpuctx between core and ibs PMU causes problems From: Peter Zijlstra To: Stephane Eranian Cc: "Yan, Zheng" , LKML , Robert Richter , mingo@elte.hu Date: Mon, 13 Aug 2012 12:28:02 +0200 In-Reply-To: References: <50235ED0.5010107@intel.com> <1344535707.20277.20.camel@twins> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1714 Lines: 57 OK,.. so the AMD IBS PMUs actually have perf_invalid_context. Lemme have a proper look... Weirdness.. perf_pmu_register() will allocate a pmu->pmu_cpu_context for each PMU. find_pmu_context() even special cases the perf_invalid_context to return NULL to force the allocation instead of sharing it. So both IBS PMUs should have their own cpuctx. In any case, I was talking about something like the below.. I hate growing the per-task ctx array with two entries, esp. since we'll mostly add two NULL pointer checks on every perf operation for everybody not using IBS. --- --- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c +++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c @@ -436,7 +436,7 @@ static void perf_ibs_read(struct perf_ev static struct perf_ibs perf_ibs_fetch = { .pmu = { - .task_ctx_nr = perf_invalid_context, + .task_ctx_nr = perf_hw2_context, .event_init = perf_ibs_init, .add = perf_ibs_add, @@ -459,7 +459,7 @@ static struct perf_ibs perf_ibs_fetch = static struct perf_ibs perf_ibs_op = { .pmu = { - .task_ctx_nr = perf_invalid_context, + .task_ctx_nr = perf_hw3_context, .event_init = perf_ibs_init, .add = perf_ibs_add, --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1237,6 +1237,8 @@ enum perf_event_task_context { perf_invalid_context = -1, perf_hw_context = 0, perf_sw_context, + perf_hw2_context, /* AMD IBS (fetch) */ + perf_hw3_context, /* AMD IBS (ops) */ perf_nr_task_contexts, }; -- 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/