From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 086A0C3F2C6 for ; Tue, 3 Mar 2020 20:29:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7C1C20CC7 for ; Tue, 3 Mar 2020 20:29:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731585AbgCCU3U (ORCPT ); Tue, 3 Mar 2020 15:29:20 -0500 Received: from mga07.intel.com ([134.134.136.100]:35388 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731014AbgCCU3U (ORCPT ); Tue, 3 Mar 2020 15:29:20 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Mar 2020 12:29:19 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,511,1574150400"; d="scan'208";a="440731143" Received: from labuser-ice-lake-client-platform.jf.intel.com ([10.54.55.45]) by fmsmga006.fm.intel.com with ESMTP; 03 Mar 2020 12:29:19 -0800 From: kan.liang@linux.intel.com To: peterz@infradead.org, mingo@redhat.com, linux-kernel@vger.kernel.org Cc: irogers@google.com, eranian@google.com, ak@linux.intel.com, Kan Liang Subject: [PATCH] perf/core: Fix endless multiplex timer Date: Tue, 3 Mar 2020 12:28:19 -0800 Message-Id: <20200303202819.3942-1-kan.liang@linux.intel.com> X-Mailer: git-send-email 2.17.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kan Liang A lot of time are spent in writing uncore MSRs even though no perf is running. 4.66% swapper [kernel.kallsyms] [k] native_write_msr | --4.56%--native_write_msr | |--1.68%--snbep_uncore_msr_enable_box | perf_mux_hrtimer_handler | __hrtimer_run_queues | hrtimer_interrupt | smp_apic_timer_interrupt | apic_timer_interrupt | cpuidle_enter_state | cpuidle_enter | do_idle | cpu_startup_entry | start_kernel | secondary_startup_64 The root cause is that multiplex timer was not stopped when perf stat finished. Current perf relies on rotate_necessary to determine whether the multiplex timer should be stopped. The variable only be reset in ctx_sched_out(), which is not enough for system-wide event. Perf stat invokes PERF_EVENT_IOC_DISABLE to stop system-wide event before closing it. perf_ioctl() perf_event_disable() event_sched_out() The rotate_necessary will never be reset. The issue is a generic issue, not just impact the uncore. Check whether we had been multiplexing. If yes, reset rotate_necessary for the last active event in __perf_event_disable(). Fixes: fd7d55172d1e ("perf/cgroups: Don't rotate events for cgroups unnecessarily") Reported-by: Andi Kleen Reviewed-by: Andi Kleen Signed-off-by: Kan Liang --- kernel/events/core.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index 3f1f77de7247..50688de56181 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2242,6 +2242,16 @@ static void __perf_event_disable(struct perf_event *event, update_cgrp_time_from_event(event); } + /* + * If we had been multiplexing, + * stop the rotations for the last active event. + * Only need to check system wide events. + * For task events, it will be checked in ctx_sched_out(). + */ + if ((cpuctx->ctx.nr_events != cpuctx->ctx.nr_active) && + (cpuctx->ctx.nr_active == 1)) + cpuctx->ctx.rotate_necessary = 0; + if (event == event->group_leader) group_sched_out(event, cpuctx, ctx); else -- 2.17.1