From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Galbraith Subject: Re: PREEMPT_RT with Full Tickless Date: Sun, 13 Dec 2015 05:19:50 +0100 Message-ID: <1449980390.3271.9.camel@gmail.com> References: <1449844577.4882.5.camel@gmail.com> <20151211175023.GN6720@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: GeHao Kang , Thomas Gleixner , Peter Zijlstra , jason.low2@hp.com, RT To: Gary Robertson , Sebastian Andrzej Siewior Return-path: Received: from mail-wm0-f42.google.com ([74.125.82.42]:32935 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751324AbbLMETy (ORCPT ); Sat, 12 Dec 2015 23:19:54 -0500 Received: by mail-wm0-f42.google.com with SMTP id n186so4312868wmn.0 for ; Sat, 12 Dec 2015 20:19:53 -0800 (PST) In-Reply-To: Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Sat, 2015-12-12 at 14:11 -0600, Gary Robertson wrote: > On Fri, Dec 11, 2015 at 11:50 AM, Sebastian Andrzej Siewior > wrote: > > * Mike Galbraith | 2015-12-11 15:36:17 [+0100]: > > > > > On Fri, 2015-12-11 at 19:29 +0800, GeHao Kang wrote: > > > > When I enable CONFIG_PREEMPT_RT_FULL and CONFIG_NO_HZ_FULL > > > > in Linux Kernel v4.1.12-rt12, I find the tick on the nohz_full > > > > cpu > > > > never stops. > > > > > > Also - since in RT the tick timer interrupt results in a schedulable > thread running to handle the software interrupt work stimulated by > the > tick - upon exit from the interrupt handler there are always at least > 2 runnable threads in the CPU running the tick if there was a > runnable > task interrupted by the tick event. Yup, handling that was one of the hacks that was dropped. If you look at what all was dropped in one 'let's con NOHZ_FULL into working' patch, you'd think twice about submitting it for review. -Mike