From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752768AbZKWOAe (ORCPT ); Mon, 23 Nov 2009 09:00:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751820AbZKWOAe (ORCPT ); Mon, 23 Nov 2009 09:00:34 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:54138 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751186AbZKWOAd (ORCPT ); Mon, 23 Nov 2009 09:00:33 -0500 Subject: [PATCH 9/8] perf_events: Restore sanity to scaling land From: Peter Zijlstra To: Ingo Molnar Cc: Paul Mackerras , linux-kernel@vger.kernel.org In-Reply-To: <20091123103722.140831906@chello.nl> References: <20091123103722.140831906@chello.nl> Content-Type: text/plain; charset="UTF-8" Date: Mon, 23 Nov 2009 15:00:36 +0100 Message-ID: <1258984836.4531.480.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It is quite possible to call update_event_times() on a context that isn't actually running and thereby confuse the thing. perf stat was reporting !100% scale values for software counters (2e2af50b perf_events: Disable events when we detach them, solved the worst of that, but there was still some left). The thing that happens is that because we are not self-reaping (we have a caring parent) there is a time between the last schedule (out) and having do_exit() called which will detach the events. This period would be accounted as enabled,!running because the event->state==INACTIVE, even though !event->ctx->is_active. Similar issues could have been observed by calling read() on a event while the attached task was not scheduled in. Solve this by teaching update_event_times() about ctx->is_active. Signed-off-by: Peter Zijlstra --- kernel/perf_event.c | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 0b0d5f7..0aafe85 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -274,7 +274,12 @@ static void update_event_times(struct perf_event *event) event->group_leader->state < PERF_EVENT_STATE_INACTIVE) return; - event->total_time_enabled = ctx->time - event->tstamp_enabled; + if (ctx->is_active) + run_end = ctx->time; + else + run_end = event->tstamp_stopped; + + event->total_time_enabled = run_end - event->tstamp_enabled; if (event->state == PERF_EVENT_STATE_INACTIVE) run_end = event->tstamp_stopped;