From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932088AbeCFFzK (ORCPT ); Tue, 6 Mar 2018 00:55:10 -0500 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:57028 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750743AbeCFFzJ (ORCPT ); Tue, 6 Mar 2018 00:55:09 -0500 Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig102.frc2.facebook.com To: , , CC: , , Song Liu Smtp-Origin-Cluster: frc2c02 Subject: [PATCH] perf: correct ctx_event_type in ctx_resched() Date: Mon, 5 Mar 2018 21:55:04 -0800 Message-ID: <20180306055504.3283731-1-songliubraving@fb.com> X-Mailer: git-send-email 2.9.5 X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-06_03:,, signatures=0 X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In ctx_resched(), EVENT_FLEXIBLE should be sched_out when EVENT_PINNED is added. However, ctx_resched() calculates ctx_event_type before checking this condition. As a result, pinned events will NOT get higher priority than flexible events. The following shows this issue on an Intel CPU (where ref-cycles can only use one hardware counter). 1. First start: perf stat -C 0 -e ref-cycles -I 1000 2. Then, in the second console, run: perf stat -C 0 -e ref-cycles:D -I 1000 The second perf uses pinned events, which is expected to have higher priority. However, because it failed in ctx_resched(). It is never run. This patch fixes this by calculating ctx_event_type after re-evaluating event_type. Fixes: 487f05e18aa4 ("perf/core: Optimize event rescheduling on active contexts") Signed-off-by: Song Liu Reported-by: Ephraim Park --- kernel/events/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 5789810..cf52fc0 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2246,7 +2246,7 @@ static void ctx_resched(struct perf_cpu_context *cpuctx, struct perf_event_context *task_ctx, enum event_type_t event_type) { - enum event_type_t ctx_event_type = event_type & EVENT_ALL; + enum event_type_t ctx_event_type; bool cpu_event = !!(event_type & EVENT_CPU); /* @@ -2256,6 +2256,8 @@ static void ctx_resched(struct perf_cpu_context *cpuctx, if (event_type & EVENT_PINNED) event_type |= EVENT_FLEXIBLE; + ctx_event_type = event_type & EVENT_ALL; + perf_pmu_disable(cpuctx->ctx.pmu); if (task_ctx) task_ctx_sched_out(cpuctx, task_ctx, event_type); -- 2.9.5