From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arjan van de Ven Subject: Re: [Results] [RFC PATCH v4 00/40] mm: Memory Power Management Date: Wed, 25 Sep 2013 18:14:19 -0700 Message-ID: <52438A6B.30202@linux.intel.com> References: <20130925231250.26184.31438.stgit@srivatsabhat.in.ibm.com> <52437128.7030402@linux.vnet.ibm.com> <20130925164057.6bbaf23bdc5057c42b2ab010@linux-foundation.org> <20130925234734.GK18242@two.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mga09.intel.com ([134.134.136.24]:57611 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751070Ab3IZBOV (ORCPT ); Wed, 25 Sep 2013 21:14:21 -0400 In-Reply-To: <20130925234734.GK18242@two.firstfloor.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Andi Kleen Cc: Andrew Morton , "Srivatsa S. Bhat" , mgorman@suse.de, dave@sr71.net, hannes@cmpxchg.org, tony.luck@intel.com, matthew.garrett@nebula.com, riel@redhat.com, srinivas.pandruvada@linux.intel.com, willy@linux.intel.com, kamezawa.hiroyu@jp.fujitsu.com, lenb@kernel.org, rjw@sisk.pl, gargankita@gmail.com, paulmck@linux.vnet.ibm.com, svaidy@linux.vnet.ibm.com, isimatu.yasuaki@jp.fujitsu.com, santosh.shilimkar@ti.com, kosaki.motohiro@gmail.com, linux-pm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On 9/25/2013 4:47 PM, Andi Kleen wrote: >> Also, the changelogs don't appear to discuss one obvious downside: the >> latency incurred in bringing a bank out of one of the low-power states >> and back into full operation. Please do discuss and quantify that to >> the best of your knowledge. > > On Sandy Bridge the memry wakeup overhead is really small. It's on by default > in most setups today. yet grouping is often defeated (in current systems) due to hw level interleaving ;-( sometimes that's a bios setting though. in internal experimental bioses we've been able to observe a "swing" of a few watts (not with these patches but with some other tricks)... I'm curious to see how these patches do for Srivatsa