Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754556AbbGJO1C (ORCPT ); Fri, 10 Jul 2015 10:27:02 -0400 Received: from cantor2.suse.de ([195.135.220.15]:35101 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754523AbbGJO0x (ORCPT ); Fri, 10 Jul 2015 10:26:53 -0400 Date: Fri, 10 Jul 2015 15:26:49 +0100 From: Mel Gorman To: Andrew Morton Cc: Nathan Zimmer , Nishanth Aravamudan , Tejun Heo , Lai Jiangshan , linux-kernel@vger.kernel.org, Eric Dumazet Subject: Re: [RFC] kthread_create_on_node is failing to honor the node choice Message-ID: <20150710142649.GX6812@suse.de> References: <20150625204855.GC26927@suse.de> <1435268653-167841-1-git-send-email-nzimmer@sgi.com> <20150709151259.2ce6a8882d0c98ae77528667@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20150709151259.2ce6a8882d0c98ae77528667@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1511 Lines: 40 On Thu, Jul 09, 2015 at 03:12:59PM -0700, Andrew Morton wrote: > On Thu, 25 Jun 2015 16:44:13 -0500 Nathan Zimmer wrote: > > > In kthread_create_on_node we set_cpus_allowed to cpu_all_mask > > regardless of what the node is requested. > > This seems incorrect. > > The `node' arg to kthread_create_on_node() refers to which node the > task_struct and thread_info are allocated from. It doesn't refer to > the CPUs upon which the thread is executed. See > kthread_create_info.node and that gruesome task_struct.pref_node_fork > thing. > That's the initial mistake I made when reviewing Nathan's first path. > The kthread_create_on_node() kerneldoc explains this, in a confused > way. It needs a s/-1/NUMA_NO_NODE/. > > I'm a bit surprised that kthread_create_on_node() futzes with the new > thread's policy and cpumask after it has been created. Wouldn't it be > simpler/faster to have the thread itself set these things while it's > starting up? > Yeah, which is what Nathan's first patch did that I made a mistake with initially. It creates a thread, sets the mask then wakes it up which looks correct. Your documentation patch looks good to me, I would not have fallen into the trap if it had been applied. -- Mel Gorman SUSE Labs -- 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/