From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754578Ab3GAQKt (ORCPT ); Mon, 1 Jul 2013 12:10:49 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:48931 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752975Ab3GAQKr (ORCPT ); Mon, 1 Jul 2013 12:10:47 -0400 Date: Mon, 1 Jul 2013 09:03:14 -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: <20130701160314.GM3773@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130628200949.GA17458@linux.vnet.ibm.com> <87a9m65mv6.fsf@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87a9m65mv6.fsf@tassilo.jf.intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13070116-7606-0000-0000-00000CF13E34 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 01, 2013 at 08:19:25AM -0700, Andi Kleen wrote: > "Paul E. McKenney" writes: > > > > The individual patches are as follows: > > > > 1. Add a CONFIG_NO_HZ_FULL_SYSIDLE Kconfig parameter to enable > > this feature. Kernels built with CONFIG_NO_HZ_FULL_SYSIDLE=n > > act exactly as they do today. > > Is this extra CONFIG option really needed? RCU already has a bewildering > variety of CONFIG options, and no idle CONFIG is also pretty complicated. > At some point noone will know how to configure kernels anymore if > these non trivial, complicated trade off CONFIGs keep spreading. > > The facility sounds like a good thing in general. Just enable > it implicitely with NO_HZ_SYSIDLE ? 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. > 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. Thanx, Paul