Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753523Ab2B0RJK (ORCPT ); Mon, 27 Feb 2012 12:09:10 -0500 Received: from e1.ny.us.ibm.com ([32.97.182.141]:46987 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753128Ab2B0RJI (ORCPT ); Mon, 27 Feb 2012 12:09:08 -0500 Date: Mon, 27 Feb 2012 09:05:27 -0800 From: "Paul E. McKenney" To: Yong Zhang Cc: Venki Pallipadi , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Suresh Siddha , Aaron Durbin , Paul Turner , linux-kernel@vger.kernel.org Subject: Re: [PATCH] Extend mwait idle to optimize away CAL and RES interrupts to an idle CPU -v1 Message-ID: <20120227170527.GD2463@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1329957415-15239-1-git-send-email-venki@google.com> <1329989454.24994.57.camel@twins> <20120224054150.GA17543@zhy> <20120226013253.GN2393@linux.vnet.ibm.com> <20120227090646.GA1112@zhy> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120227090646.GA1112@zhy> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12022717-6078-0000-0000-0000087B911F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1585 Lines: 37 On Mon, Feb 27, 2012 at 05:06:46PM +0800, Yong Zhang wrote: > On Sat, Feb 25, 2012 at 05:32:53PM -0800, Paul E. McKenney wrote: > > On Fri, Feb 24, 2012 at 01:41:50PM +0800, Yong Zhang wrote: > > > On Thu, Feb 23, 2012 at 11:34:11AM -0800, Venki Pallipadi wrote: > > > > On Thu, Feb 23, 2012 at 1:30 AM, Peter Zijlstra wrote: > > > > > Why not scheduler_ipi()? > > > > > > > > Was trying to avoid irq_enter/exit. As the work here is done in idle > > > > thread context, I though we could avoid enter/exit. > > > > > > It seems we could not. > > > At least RCU need it, see commit c5d753a55, otherwise we will get > > > warning like 'RCU used illegally from extended quiescent state!' > > > > If the use is tracing, then Steven Rostedt's patchset plus use of his > > _rcuidle() tracing variants handles this: > > > > https://lkml.org/lkml/2012/2/7/231 > > > > If this is instead algorithmic use of RCU, a set of patches I have queued > > up for 3.4 will be required. > > scheduler_ipi() doing more than tracing. Will look at your patches :) Ah! The key question is whether or not the code in question is called both from idle and from non-idle. This will be easiest if the code is called only from idle, in which case you should only need this one: https://lkml.org/lkml/2012/2/3/498 Thanx, Paul -- 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/