From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Bristot de Oliveira Subject: Re: Kernel thread's CPU affinity with isolcpus kernel boot argument Date: Thu, 25 Feb 2016 12:13:46 -0300 Message-ID: <56CF1A2A.1050203@bristot.me> References: <5698D4D0.3020907@etas.com> <20160225141806.GB16161@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: "linux-rt-users@vger.kernel.org" To: Sebastian Andrzej Siewior , Mathias Koehrer Return-path: Received: from smtpi-sp-245.kinghost.net ([177.185.201.245]:50945 "EHLO smtpi-sp-245.kinghost.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932337AbcBYPVs (ORCPT ); Thu, 25 Feb 2016 10:21:48 -0500 In-Reply-To: <20160225141806.GB16161@linutronix.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 02/25/2016 11:18 AM, Sebastian Andrzej Siewior wrote: > not that I am aware of. There are a few per-CPU threads which have to > stay the way they are. I would have expected that others like kworker/u* > respect the isol CPUs and stay away. Isolcpus is applied only for user-space threads. For instance, you still need to move rcu offload callbacks away from isolated CPUs, and all other kernel threads as well. In the special case of kworker/u* threads, you need to use a special interface to do it. The interface is the following file: /sys/devices/virtual/workqueue/cpumask It was implemented on the following commit: 042f7df workqueue: Allow modifying low level unbound workqueue cpumask But the default CPU mask is the "cpu_possible_mask". Sometime ago I sent a patch to modify the default mask of the kworker/u* threads, to avoid them on isolated CPUs by default, but it was not acked. It was not explicitly nacked, though. http://www.gossamer-threads.com/lists/linux/kernel/2218495 Should I try it again? -- Daniel