Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751840AbbLLOQw (ORCPT ); Sat, 12 Dec 2015 09:16:52 -0500 Received: from mail-qk0-f171.google.com ([209.85.220.171]:33619 "EHLO mail-qk0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750941AbbLLOQu (ORCPT ); Sat, 12 Dec 2015 09:16:50 -0500 MIME-Version: 1.0 In-Reply-To: <1449903863.9638.8.camel@gmail.com> References: <1449903863.9638.8.camel@gmail.com> Date: Sat, 12 Dec 2015 15:16:50 +0100 Message-ID: Subject: Re: sched : performance regression 24% between 4.4rc4 and 4.3 kernel From: Jirka Hladky To: Mike Galbraith Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Rik van Riel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2257 Lines: 52 > A bisection doesn't require any special skills, but may give busy > maintainers a single change to eyeball vs the entire lot. They have been couple of merges which makes git revert difficult but I will try to produce patch files for kernel/sched directory only with git diff v4.4-rc4..fe19159 -- sched and let you the outcome. On Sat, Dec 12, 2015 at 8:04 AM, Mike Galbraith wrote: > (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/