Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755148Ab3DOQGF (ORCPT ); Mon, 15 Apr 2013 12:06:05 -0400 Received: from a9-58.smtp-out.amazonses.com ([54.240.9.58]:41432 "EHLO a9-58.smtp-out.amazonses.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753635Ab3DOQGD (ORCPT ); Mon, 15 Apr 2013 12:06:03 -0400 X-Greylist: delayed 355 seconds by postgrey-1.27 at vger.kernel.org; Mon, 15 Apr 2013 12:06:02 EDT Date: Mon, 15 Apr 2013 16:00:04 +0000 From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Arjan van de Ven cc: paulmck@linux.vnet.ibm.com, 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 Subject: Re: [PATCH documentation 1/2] nohz1: Add documentation. In-Reply-To: <51684AD3.7090305@linux.intel.com> Message-ID: <0000013e0e6cacbb-b7e44c6f-d551-49b9-aa07-62a4ee280ae7-000000@email.amazonses.com> 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> <51684AD3.7090305@linux.intel.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-SES-Outgoing: 2013.04.15-54.240.9.58 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 928 Lines: 21 On Fri, 12 Apr 2013, Arjan van de Ven wrote: > 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) If we are able to only get rid of one timer tick on average with dynticks then I would think that is enough to justify having it on by default. If the scheduling period from the schduler is around 20ms then one may be able to save processing 20 timer ticks by going to htimers. The main issue with hrtimers is likely going to be that is it is too much effort for small timerframes less than 10ms. Could we only switch off the timer tick if the next event is more than 10 ticks aways? -- 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/