Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756216Ab3DLR4i (ORCPT ); Fri, 12 Apr 2013 13:56:38 -0400 Received: from mga09.intel.com ([134.134.136.24]:38090 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752884Ab3DLR4h (ORCPT ); Fri, 12 Apr 2013 13:56:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,464,1363158000"; d="scan'208";a="317361288" Message-ID: <51684AD3.7090305@linux.intel.com> Date: Fri, 12 Apr 2013 10:56:35 -0700 From: Arjan van de Ven User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Peter Zijlstra , Borislav Petkov , linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, Kevin Hilman , Christoph Lameter Subject: Re: [PATCH documentation 1/2] nohz1: Add documentation. References: <20130411160524.GA30384@linux.vnet.ibm.com> <1365696359-30958-1-git-send-email-paulmck@linux.vnet.ibm.com> <20130411182502.GA31684@pd.tnic> <20130411191355.GO29861@linux.vnet.ibm.com> <1365753904.17140.22.camel@laptop> <20130412175419.GG29861@linux.vnet.ibm.com> In-Reply-To: <20130412175419.GG29861@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 878 Lines: 22 > ------------------------------------------------------------------------ > > 1. It increases the number of instructions executed on the path > to and from the idle loop. > > 2. On many architectures, dyntick-idle mode also increases the > number of times that clocks must be reprogrammed, and this > reprogramming can be quite expensive. it's really that we're no longer using periodic clocks, but only one-shot clocks only. (which then leads to having to program them every time) but arguably, that's because of HRTIMERS more than NOHZ (e.g. I bet we still turn off periodic even for nohz as long as hrtimers are enabled) -- 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/