From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751017AbdFSPPc (ORCPT ); Mon, 19 Jun 2017 11:15:32 -0400 Received: from foss.arm.com ([217.140.101.70]:51434 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750780AbdFSPPb (ORCPT ); Mon, 19 Jun 2017 11:15:31 -0400 Date: Mon, 19 Jun 2017 16:14:41 +0100 From: Mark Rutland To: Alexey Budankov Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Andi Kleen , Kan Liang , Dmitri Prokhorov , Valery Cherepennikov , David Carrillo-Cisneros , Stephane Eranian , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/n] perf/core: addressing 4x slowdown during per-process profiling of STREAM benchmark on Intel Xeon Phi Message-ID: <20170619151441.GB4555@leverpostej> References: <09226446-39b9-9bd2-d60f-b9bb947987c5@linux.intel.com> <20170615195618.GA8807@leverpostej> <07a76338-4c71-569a-d36e-7d6bcd10bd74@linux.intel.com> <20170619132652.GA3894@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 19, 2017 at 04:37:41PM +0300, Alexey Budankov wrote: > On 19.06.2017 16:26, Mark Rutland wrote: > >On Mon, Jun 19, 2017 at 04:08:32PM +0300, Alexey Budankov wrote: > >>On 16.06.2017 1:10, Alexey Budankov wrote: > >>>On 15.06.2017 22:56, Mark Rutland wrote: > >>>>On Thu, Jun 15, 2017 at 08:41:42PM +0300, Alexey Budankov wrote: > >>>>>This series of patches continues v2 and addresses captured comments. > > > >>>>>Specifically this patch replaces pinned_groups and flexible_groups > >>>>>lists of perf_event_context by red-black cpu indexed trees avoiding > >>>>>data structures duplication and introducing possibility to iterate > >>>>>event groups for a specific CPU only. > > > >>>>Have you thrown Vince's perf fuzzer at this? > >>>> > >>>>If you haven't, please do. It can be found in the fuzzer directory of: > >>>> > >>>>https://github.com/deater/perf_event_tests > >>> > >>>Accepted. > >> > >>I run the test suite and it revealed no additional regressions in > >>comparison to what I have on the clean kernel. > >> > >>However the fuzzer constantly reports some strange stacks that are > >>not seen on the clean kernel and I have no idea how that might be > >>caused by the patches. > > > >Ok; that was the kind of thing I was concerned about. > > > >What you say "strange stacks", what do you mean exactly? > > > >I take it the kernel spewing backtraces in dmesg? > > > >Can you dump those? > > Here it is: > > list_del corruption. prev->next should be ffff88c2c4654010, but was > ffff88c31eb0c020 > [ 607.632813] ------------[ cut here ]------------ > [ 607.632816] kernel BUG at lib/list_debug.c:53! > [ 607.635531] Call Trace: > [ 607.635583] list_del_event+0x1d7/0x210 Given this patch changes how list_{del,add}_event() works, it's possible that this is a new bug. I was going to try to test this on arm64, but I couldn't get the patch to apply. I had a go with v4.12-rc5, tip/perf/core, and tip/perf/urgent. Which branch should I be using as the base? Thanks, Mark