From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754971Ab0IQCHW (ORCPT ); Thu, 16 Sep 2010 22:07:22 -0400 Received: from mga11.intel.com ([192.55.52.93]:15120 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753204Ab0IQCHV (ORCPT ); Thu, 16 Sep 2010 22:07:21 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.56,380,1280732400"; d="scan'208";a="838431286" Subject: Re: high power consumption in recent kernels From: "Alex,Shi" To: Norbert Preining Cc: Peter Zijlstra , "Chen, Tim C" , "arjan@infradead.org" , "efault@gmx.de" , "Li, Shaohua" , tglx , "linux-kernel@vger.kernel.org" In-Reply-To: <1284355277.26157.8109.camel@debian> References: <1283840425.26157.6486.camel@debian> <20100909093140.GC29648@gamma.logic.tuwien.ac.at> <20100909205115.GD11053@gamma.logic.tuwien.ac.at> <1284107099.402.30.camel@laptop> <6E3BC7F7C9A4BF4286DD4C043110F30B2991AF14FD@shsmsx502.ccr.corp.intel.com> <20100910145451.GB21450@gamma.logic.tuwien.ac.at> <1284355277.26157.8109.camel@debian> Content-Type: text/plain; charset="UTF-8" Date: Fri, 17 Sep 2010 10:09:34 +0800 Message-ID: <1284689374.17745.89.camel@debian> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > - how to reduce the "extra timer interrupt"? > The timer was listed in /proc/timer_stats, you can post its contents, > and let's see what is abnormal here. > Norbert, did you try the patch? We are still thinking the too many "extra timer interrupts" on your system, maybe the following message can give some help. So, could you like to check if your system is using pit timer? #cat /proc/timer_list Or some APP/system services in your system is using lots of timer? === http://www.linuxpowertop.org/faq.php Even with a tickless kernel, there are some timer ticks still happening: 1.) For userspace events (also shown in the lower "top 10 events" list). 2.) The kernel still has timer ticks when userspace is executing code, to sample and get data for the "top" program. 3.) Hardware timers have a maximum time they can be set for, for the PIT timer (the one used if you don't have HPET active). This is around 27 milliseconds. If you would have longer sleep times than the maximum, the kernel has no choice but to set the timer to the maximum repeatedly until the actual event is approaching. The "extra timer interrupts" data is a combination fo 1 and 3.