From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753308Ab2GTRCK (ORCPT ); Fri, 20 Jul 2012 13:02:10 -0400 Received: from merlin.infradead.org ([205.233.59.134]:50197 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753122Ab2GTRCI convert rfc822-to-8bit (ORCPT ); Fri, 20 Jul 2012 13:02:08 -0400 Message-ID: <1342803700.2583.29.camel@twins> Subject: Re: [PATCHSET] workqueue: reimplement CPU hotplug to keep idle workers From: Peter Zijlstra To: Tejun Heo Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, tglx@linutronix.de, linux-pm@vger.kernel.org Date: Fri, 20 Jul 2012 19:01:40 +0200 In-Reply-To: <20120720165213.GD32763@google.com> References: <1342545149-3515-1-git-send-email-tj@kernel.org> <1342802391.2583.11.camel@twins> <20120720165213.GD32763@google.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-07-20 at 09:52 -0700, Tejun Heo wrote: > Ooh, yeah, I agree. That's next on the wq to-do list. The problem is > that queue_work() is implemented in terms of queue_work_on(). But that's trivial to fix, both could use __queue_work() without too much bother, right? > In most > cases, the local binding serves as locality optimization than anything > else. There are use cases where affinity is required for correctness. > The assumption was that they should flush during CPU_DOWN but it > probably will be much better to require users which need CPU affinity > to always use queue_work_on() - instead of implicit local affinity > from queue_work() - and flush them automatically from wq callback. > Right, and when you create this new mode, which you need to know to flush on DOWN, you can simply put a BUG_ON in queue_work_on() when this mode is set.