Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751309AbbLLHE2 (ORCPT ); Sat, 12 Dec 2015 02:04:28 -0500 Received: from mail-wm0-f48.google.com ([74.125.82.48]:37459 "EHLO mail-wm0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751043AbbLLHE1 (ORCPT ); Sat, 12 Dec 2015 02:04:27 -0500 Message-ID: <1449903863.9638.8.camel@gmail.com> Subject: Re: sched : performance regression 24% between 4.4rc4 and 4.3 kernel From: Mike Galbraith To: Jirka Hladky , linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar Date: Sat, 12 Dec 2015 08:04:23 +0100 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1801 Lines: 38 (it's always a good idea to CC subsystem maintainers when reporting) On Fri, 2015-12-11 at 15:17 +0100, Jirka Hladky wrote: > Hello, > > we are doing performance testing of the new kernel scheduler (commit > 53528695ff6d8b77011bc818407c13e30914a946). In most cases we see > performance improvements compared to 4.3 kernel with the exception of > stream benchmark when running on 4 NUMA node server. > > When we run 4 stream benchmark processes on 4 NUMA node server and we > compare the total performance we see drop about 24% compared to 4.3 > kernel. This is caused by the fact that 2 stream benchmarks are > running on the same NUMA node while 1 NUMA node does not run any > stream benchmark. With kernel 4.3, load is distributed evenly among > all 4 NUMA nodes. When two stream benchmarks are running on the same > NUMA node then the runtime is almost twice as long compared to one > stream bench running on one NUMA node. See log files [1] bellow. > > Please see the graph comparing stream benchmark results between > kernel > 4.3 and 4.4rc4 (for legend see [2] bellow). > https://jhladky.fedorapeople.org/sched_stream_kernel_4.3vs4.4rc4/Stre > am_benchmark_on_4_NUMA_node_server_4.3vs4.4rc4_kernel.png > > Could you please help us to identify the root cause of this > regression? We don't have the skills to fix the problem ourselves but > we will be more than happy to test any proposed patch for this issue. A bisection doesn't require any special skills, but may give busy maintainers a single change to eyeball vs the entire lot. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/