Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754327Ab3CVE74 (ORCPT ); Fri, 22 Mar 2013 00:59:56 -0400 Received: from mail-ie0-f176.google.com ([209.85.223.176]:57266 "EHLO mail-ie0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752680Ab3CVE7z convert rfc822-to-8bit (ORCPT ); Fri, 22 Mar 2013 00:59:55 -0400 Date: Thu, 21 Mar 2013 23:59:50 -0500 From: Rob Landley Subject: Re: [PATCH] nohz1: Documentation To: Arjan van de Ven Cc: Steven Rostedt , paulmck@linux.vnet.ibm.com, Frederic Weisbecker , linux-kernel@vger.kernel.org, josh@joshtriplett.org, zhong@linux.vnet.ibm.com, khilman@linaro.org, geoff@infradead.org, tglx@linutronix.de In-Reply-To: <514B2B03.4030301@linux.intel.com> (from arjan@linux.intel.com on Thu Mar 21 10:45:07 2013) X-Mailer: Balsa 2.4.11 Message-Id: <1363928390.15703.57@driftwood> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; DelSp=Yes; Format=Flowed Content-Disposition: inline Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1243 Lines: 34 On 03/21/2013 10:45:07 AM, Arjan van de Ven wrote: > On 3/20/2013 5:27 PM, Steven Rostedt wrote: >> I'm not sure I would recommend idle=poll either. It would certainly >> work, but it goes to the other extreme. You think NO_HZ=n drains a >> battery? Try idle=poll. > > > do not ever use idle=poll on anything production.. really bad idea. > > if you temporary cannot cope with the latency, you can use the PMQOS > system > to limit (including going all the way to idle=poll). > but using idle=poll completely is very nasty for the hardware. > > In addition we should document that idle=poll will cost you peak > performance, > possibly quite a bit. Where should that be documented? > the same is true for the kernel paramter to some extend; it's there > to work around > broken bioses/hardware/etc; if you have a latency/runtime > requirement, it's much better > to use PMQOS for this from userspace. I googled and found http://elinux.org/images/f/f9/Elc2008_pm_qos_slides.pdf Rob-- 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/