From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756074AbcAMShR (ORCPT ); Wed, 13 Jan 2016 13:37:17 -0500 Received: from comal.ext.ti.com ([198.47.26.152]:40242 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751255AbcAMShP (ORCPT ); Wed, 13 Jan 2016 13:37:15 -0500 Subject: Re: [ANNOUNCE] 4.4-rc6-rt1 To: Sebastian Andrzej Siewior , Mike Galbraith , References: <20151223225755.GA21121@linutronix.de> <20151231102441.581ce1e1@sluggy.hsv.redhat.com> <1451632781.9800.22.camel@gmail.com> <20160113175845.GK29964@linutronix.de> CC: Clark Williams , Thomas Gleixner , LKML , linux-rt-users , Steven Rostedt From: Grygorii Strashko Message-ID: <56969948.2060009@ti.com> Date: Wed, 13 Jan 2016 20:36:56 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <20160113175845.GK29964@linutronix.de> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/13/2016 07:58 PM, Sebastian Andrzej Siewior wrote: > * Mike Galbraith | 2016-01-01 08:19:41 [+0100]: > >>> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND >>> 3 root -2 0 0 0 0 S 37.3 0.0 307:52.44 ksoftirqd/0 >>> 32 root -2 0 0 0 0 S 37.3 0.0 308:08.72 ksoftirqd/2 >>> 42 root -2 0 0 0 0 R 37.3 0.0 308:32.84 ksoftirqd/3 >>> 22 root -2 0 0 0 0 S 26.9 0.0 222:29.82 ksoftirqd/1 >>> 1 root 20 0 46628 6980 4976 S 1.3 0.2 0:13.98 systemd >>> 22358 williams 20 0 159980 4552 3780 R 1.0 0.1 0:00.39 top >> >> Heh, I didn't notice immediately because I throttle nohz, am seeing >> only tiny utilization (but nohz idle isn't working). With throttle >> patch removed, box is screaming, expires=4294990471 pokes eyeball. > > This is due to NO_HZ as far as I can tell. My AMD A10 in idle mode has > 0.7% utilisation of ksoftirqd/ with CONFIG_HZ_PERIODIC and with > CONFIG_NO_HZ_FULL it shows about 25% on all CPU threads. > I might be wrong completely, but could below two patches affect on CPU utilization of ksoftirqd? 6047967 ksoftirqd: Use new cond_resched_rcu_qs() function 28423ad ksoftirqd: Enable IRQs and call cond_resched() before poking RCU above two patches are not applied on -RT part of softirqs processing. static void run_ksoftirqd(unsigned int cpu) { local_irq_disable(); current->softirq_nestcnt++; do_current_softirqs(); current->softirq_nestcnt--; rcu_note_context_switch(); ^^^ IRQs disabled local_irq_enable(); } -- regards, -grygorii