From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751879Ab3LKDJI (ORCPT ); Tue, 10 Dec 2013 22:09:08 -0500 Received: from zill.ext.symas.net ([69.43.206.106]:32878 "EHLO zill.ext.symas.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751564Ab3LKDJF (ORCPT ); Tue, 10 Dec 2013 22:09:05 -0500 Message-ID: <52A7D74D.7000804@symas.com> Date: Tue, 10 Dec 2013 19:09:01 -0800 From: Howard Chu User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:27.0) Gecko/20100101 Firefox/27.0 SeaMonkey/2.24a1 MIME-Version: 1.0 To: Li Zefan CC: Linux Kernel Mailing List Subject: Re: sched: RT throttling activated, 3.12.3 References: <52A7D512.5050801@symas.com> <52A7D5E5.3070704@huawei.com> In-Reply-To: <52A7D5E5.3070704@huawei.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Li Zefan wrote: > On 2013/12/11 10:59, Howard Chu wrote: >> I just upgraded a system from a 3.5 kernel to 3.12.3 and attempted to run some new benchmarks on it. I see my test program ramps up in CPU usage for a few seconds and then it gradually tails off. There's nothing obvious in the user code to trigger this behavior, so I check dmesg, and see this: >> >> [ 55.037057] JFS: nTxBlock = 8192, nTxLock = 65536 >> [163591.807470] perf samples too long (2758 > 2500), lowering kernel.perf_event_max_sample_rate to 50000 >> [164061.362762] perf samples too long (5204 > 5000), lowering kernel.perf_event_max_sample_rate to 25000 >> [167969.339513] [sched_delayed] sched: RT throttling activated >> [182741.484637] perf samples too long (294588 > 10000), lowering kernel.perf_event_max_sample_rate to 12500 >> [182741.484726] INFO: NMI handler (perf_event_nmi_handler) took too long to run: 36.665 msecs >> [182822.633084] perf samples too long (292359 > 20000), lowering kernel.perf_event_max_sample_rate to 6250 >> [182905.606119] perf samples too long (290291 > 40000), lowering kernel.perf_event_max_sample_rate to 3250 >> [199384.293514] perf samples too long (288142 > 76923), lowering kernel.perf_event_max_sample_rate to 1750 >> [208507.301027] perf samples too long (285964 > 142857), lowering kernel.perf_event_max_sample_rate to 1000 >> [208528.976208] perf samples too long (283799 > 250000), lowering kernel.perf_event_max_sample_rate to 500 >> >> Why is the kernel throttling my server? >> > > Because that is the default setting of the kernel. Apparently a "new" default that didn't exist in 3.5? The code in question is not a realtime process. This behavior also wasn't seen in 3.10 or any older kernels. > lxc34:/proc/sys/kernel # cat sched_rt_period_us > 1000000 > lxc34:/proc/sys/kernel # cat sched_rt_runtime_us > 950000 > > -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/