From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933550AbaFCSoc (ORCPT ); Tue, 3 Jun 2014 14:44:32 -0400 Received: from mail-vc0-f176.google.com ([209.85.220.176]:60070 "EHLO mail-vc0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753924AbaFCSob (ORCPT ); Tue, 3 Jun 2014 14:44:31 -0400 MIME-Version: 1.0 In-Reply-To: <20140603182850.GJ16155@laptop.programming.kicks-ass.net> References: <20140522130931.GV13658@twins.programming.kicks-ass.net> <20140529064827.GI19143@laptop.programming.kicks-ass.net> <20140603104347.GT11096@twins.programming.kicks-ass.net> <20140603140223.GA13658@twins.programming.kicks-ass.net> <20140603161950.GB30445@twins.programming.kicks-ass.net> <20140603170018.GD30445@twins.programming.kicks-ass.net> <20140603182850.GJ16155@laptop.programming.kicks-ass.net> From: Andy Lutomirski Date: Tue, 3 Jun 2014 11:44:10 -0700 Message-ID: Subject: Re: [RFC][PATCH 0/8] sched,idle: need resched polling rework To: Peter Zijlstra Cc: Ingo Molnar , Thomas Gleixner , nicolas.pitre@linaro.org, Daniel Lezcano , Mike Galbraith , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 3, 2014 at 11:28 AM, Peter Zijlstra wrote: > On Tue, Jun 03, 2014 at 07:00:18PM +0200, Peter Zijlstra wrote: >> On Tue, Jun 03, 2014 at 09:52:22AM -0700, Andy Lutomirski wrote: >> > > So you could cheat and set it in pick_next_task_idle() and clear in >> > > put_prev_task_idle(), that way the entire idle loop, when running has it >> > > set. >> > > >> > >> > Isn't that a little late for sched_ttwu_pending? I guess it could be >> > okay, but I'm hesitant to muck around with the scheduler innards that >> > much. I don't see anything that'll break, though. >> >> Yeah, only later did I see you clear much earlier, which makes sense. > > Could we clear it from set_nr_and_not_polling()/set_nr_if_polling()? > That's the only two functions that'll kick a cpu out of its polling > loop, and we're already writing to the word anyhow. I'd be nervous about this. I think it could break if cpuidle_idle_call decides not to idle for any reason, and there is plenty of complicated code in there. I'm currently working on some patches that might make this clearer. Give me a bit. --Andy -- Andy Lutomirski AMA Capital Management, LLC