Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751511AbdGRMN1 (ORCPT ); Tue, 18 Jul 2017 08:13:27 -0400 Received: from mail-wr0-f177.google.com ([209.85.128.177]:34951 "EHLO mail-wr0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751322AbdGRMN0 (ORCPT ); Tue, 18 Jul 2017 08:13:26 -0400 Date: Tue, 18 Jul 2017 14:13:22 +0200 From: Ingo Molnar To: Alexander Shishkin Cc: Vince Weaver , linux-kernel@vger.kernel.org, Peter Zijlstra , Stephane Eranian Subject: Re: perf: bisected sampling bug in Linux 4.11-rc1 Message-ID: <20170718121321.6l4ia2cw25eetpvh@gmail.com> References: <87lgnmvw7h.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87lgnmvw7h.fsf@ashishki-desk.ger.corp.intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1919 Lines: 53 * Alexander Shishkin wrote: > Vince Weaver writes: > > > I was tracking down some regressions in my perf_event_test testsuite. > > Some of the tests broke in the 4.11-rc1 timeframe. > > > > I've bisected one of them, this report is about > > tests/overflow/simul_oneshot_group_overflow > > This test creates an event group containing two sampling events, set > > to overflow to a signal handler (which disables and then refreshes the > > event). > > > > On a good kernel you get the following: > > Event perf::instructions with period 1000000 > > Event perf::instructions with period 2000000 > > fd 3 overflows: 946 (perf::instructions/1000000) > > fd 4 overflows: 473 (perf::instructions/2000000) > > Ending counts: > > Count 0: 946379875 > > Count 1: 946365218 > > > > With the broken kernels you get: > > Event perf::instructions with period 1000000 > > Event perf::instructions with period 2000000 > > fd 3 overflows: 938 (perf::instructions/1000000) > > fd 4 overflows: 318 (perf::instructions/2000000) > > Ending counts: > > Count 0: 946373080 > > Count 1: 653373058 > > > > > > 487f05e18aa4efacee6357480f293a5afe6593b5 is the first bad commit > > > > commit 487f05e18aa4efacee6357480f293a5afe6593b5 > > Author: Alexander Shishkin > > Date: Thu Jan 19 18:43:30 2017 +0200 > > Ok, there was a bug there indeed. This patch should take care of it and > should also be backportable in case it's stable-worthy. > > From 187d67c9908cb126656c34546772089c17a8e6c5 Mon Sep 17 00:00:00 2001 > From: Alexander Shishkin > Date: Tue, 18 Jul 2017 13:53:01 +0300 > Subject: [PATCH] perf: Fix scheduling regression of pinned groups Ok, great - if this works then I'll pick up this fix instead of the revert that I've queued up earlier today. Thanks, Ingo