Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757967Ab0GHP7x (ORCPT ); Thu, 8 Jul 2010 11:59:53 -0400 Received: from casper.infradead.org ([85.118.1.10]:43846 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757870Ab0GHP7w convert rfc822-to-8bit (ORCPT ); Thu, 8 Jul 2010 11:59:52 -0400 Subject: Re: high power consumption in recent kernels From: Peter Zijlstra To: Norbert Preining Cc: Arjan van de Ven , linux-kernel@vger.kernel.org, Ingo Molnar , akpm , Mike Galbraith , tglx In-Reply-To: <1278595426.1900.130.camel@laptop> References: <20100706164539.GA14783@gamma.logic.tuwien.ac.at> <1278579992.1900.17.camel@laptop> <20100708045711.398d4e26@infradead.org> <1278590303.1900.91.camel@laptop> <20100708120421.GF20841@gamma.logic.tuwien.ac.at> <1278591779.1900.97.camel@laptop> <20100708124627.GA7754@gamma.logic.tuwien.ac.at> <1278595426.1900.130.camel@laptop> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Thu, 08 Jul 2010 17:59:39 +0200 Message-ID: <1278604779.1900.157.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1309 Lines: 27 On Thu, 2010-07-08 at 15:23 +0200, Peter Zijlstra wrote: > On Thu, 2010-07-08 at 21:46 +0900, Norbert Preining wrote: > > Looks promising, reverting the old patch, adding that one, building, > > running, unplugging ppower, powertop runs now since some time, > > it seems that we are back to better situation: > > Hrmm, Mike seems you wrecked power usage.. > > So nohz_ratelimit() prevents us from entering NOHZ when the last attempt > was less than 1/2 a jiffy ago (fwiw: NSEC_PER_SEC/HZ == TICK_NSEC). > > Its either entering idle or irq_exit trying to enter nohz state, if we > keep skipping it it means that we get enough interrupt activity to > render nohz useless anyway.. so not quite sure how this wrecks things.. OK, so Arjan said the gain could come from tricking the idle governor into not using deeper C states. He also said he significantly cured said governor in .35. Mike could you re-run your netperf tests that showed the 10% throughput gain? Hopefully the fixed governor will yield the same result and we can kill off this ratelimit thing. -- 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/