Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754539AbZCCMW3 (ORCPT ); Tue, 3 Mar 2009 07:22:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751416AbZCCMWT (ORCPT ); Tue, 3 Mar 2009 07:22:19 -0500 Received: from casper.infradead.org ([85.118.1.10]:35164 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751183AbZCCMWT (ORCPT ); Tue, 3 Mar 2009 07:22:19 -0500 Subject: Re: [PATCH v2 0/3] sched: Extend sched_mc/smt_power_savings framework From: Peter Zijlstra To: Gautham R Shenoy Cc: Vaidyanathan Srinivasan , Balbir Singh , Ingo Molnar , Suresh Siddha , Dipankar Sarma , efault@gmx.de, andi@firstfloor.org, linux-kernel@vger.kernel.org In-Reply-To: <20090303114648.605.86920.stgit@sofia.in.ibm.com> References: <20090303114648.605.86920.stgit@sofia.in.ibm.com> Content-Type: text/plain Date: Tue, 03 Mar 2009 13:21:57 +0100 Message-Id: <1236082917.5330.4195.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.25.91 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3922 Lines: 75 On Tue, 2009-03-03 at 17:21 +0530, Gautham R Shenoy wrote: > Background > ------------------------------------------------------------------ > On machines with on-chip memory controller, each physical CPU > package forms a NUMA node and the CPU level sched_domain will have > only one group. This prevents any form of power saving balance across > these nodes. Enabling the sched_mc_power_savings tunable to work as > designed on these new single CPU NUMA node machines will help task > consolidation and save power as we did in other multi core multi > socket platforms. > > Consolidation across NODES have implications of cross-node memory > access and other NUMA locality issues. Even under such constraints > there could be scope for power savings vs performance tradeoffs and > hence making the sched_mc_powersavings work as expected on these > platform is justified. > > sched_mc/smt_power_savings is still a tunable and power savings benefits > and performance would vary depending on the workload and the system > topology and hardware features. > > The patch series has been tested on a 2-Socket Quad-core Dual threaded > box with kernbench as the workload, varying the number of threads. > > +------------------------------------------------------------------------+ > |Test: make -j8 | > +-----------+----------+--------+---------+-------------+----------------+ > | sched_smt | sched_mc | %Power | Time | % Package 0 | % Package 1 | > | | | | | idle | idle | > +-----------+----------+--------+---------+-------------+----------------+ > | | | | |Core0: 18.17 |Core4: 33.38 | > | | | | +-------------+----------------+ > | | | | |Core1: 34.62 |Core5: 19.58 | > | 0 | 0 | 100 | 63.82 +-------------+----------------+ > | | | | |Core2: 31.99 |Core6: 32.35 | > | | | | +-------------+----------------+ > | | | | |Core3: 34.59 |Core7: 29.99 | > +-----------+----------+--------+---------+-------------+----------------+ > +-----------+----------+--------+---------+-------------+----------------+ > | | | | |Core0: 16.65 |Core4: 79.04 | > | | | | +-------------+----------------+ > | | | | |Core1: 26.74 |Core5: 50.98 | > | 2 | 2 | 89.58 | 82.83 +-------------+----------------+ > | | | | |Core2: 30.42 |Core6: 81.33 | > | | | | +-------------+----------------+ > | | | | |Core3: 35.57 |Core7: 90.03 | > +-----------+----------+--------+---------+-------------+----------------+ So while we take longer (~20s) we save about 10% in power? It would be good to mention something about how power usage is measured. Furthermore, do we really need those separate mc/smt power savings settings? -- It appears to me we ought to consolidate some of that and provide a single knob to save power. > --- > > Gautham R Shenoy (3): > sched: Fix sd_parent_degenerate for SD_POWERSAVINGS_BALANCE. > sched: Fix the wakeup nomination for sched_mc/smt_power_savings. > sched: code cleanup - sd_power_saving_flags(), sd_balance_for_mc/package_power() Acked-by: Peter Zijlstra A few nits on patch #2, please follow up with incremental cleanups. -- 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/