From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754962Ab3GATT7 (ORCPT ); Mon, 1 Jul 2013 15:19:59 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:51051 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752864Ab3GATT6 (ORCPT ); Mon, 1 Jul 2013 15:19:58 -0400 Date: Mon, 1 Jul 2013 12:19:49 -0700 From: "Paul E. McKenney" To: Andi Kleen Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu Subject: Re: [PATCH RFC nohz_full 0/7] v2 Provide infrastructure for full-system idle Message-ID: <20130701191949.GS3773@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130628200949.GA17458@linux.vnet.ibm.com> <87a9m65mv6.fsf@tassilo.jf.intel.com> <20130701160314.GM3773@linux.vnet.ibm.com> <20130701161910.GN6123@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130701161910.GN6123@two.firstfloor.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13070119-7182-0000-0000-000007986AED Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 01, 2013 at 06:19:10PM +0200, Andi Kleen wrote: > > I am guessing that you want CONFIG_NO_HZ_FULL to implicitly enable > > the sysidle code so that CONFIG_NO_HZ_FULL_SYSIDLE can be eliminated. > > I will be happy to take that step, but only after I gain full confidence > > in the correctness and performance of the sysidle code. > > FWIW if you want useful testing you need to enable it by default > (as part of NO_IDLE_HZ) anyways. Users will most likely pick > whatever is "default" in Kconfig. At this point in the process, I want testers who choose to test. Hapless victim testers come later. Well, other than randconfig testers, but I consider them to be voluntary hapless victims. ;-) > > > If you want a switch for testing I would advise a sysctl or sysfs knob > > > > This would work well for the correctness part, but not for the performance > > part. > > What performance part? > > Are you saying this adds so many checks to hot paths that normal runtime > if() with a flag is too expensive? I am saying that I don't know, and that I want to make it easy for people to find out by comparing to the base configuration -- and for me to be able to detect this from their .config file. Thanx, Paul