From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932193Ab2AIPn4 (ORCPT ); Mon, 9 Jan 2012 10:43:56 -0500 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:56846 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932152Ab2AIPnz (ORCPT ); Mon, 9 Jan 2012 10:43:55 -0500 X-Sasl-enc: /TZCjW858Zek93U7s0a84yeEmZzmaMgirtBRbkNA9Lir 1326123833 Date: Mon, 9 Jan 2012 07:37:58 -0800 From: Greg KH To: Youquan Song Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, a.p.zijlstra@chello.nl, tglx@linutronix.de, hpa@zytor.com, akpm@linux-foundation.org, stable@vger.kernel.org, suresh.b.siddha@intel.com, arjan@linux.intel.com, len.brown@intel.com, anhua.xu@intel.com, chaohong.guo@intel.com, Youquan Song Subject: Re: [PATCH] x86,sched: Fix sched_smt_power_savings totally broken Message-ID: <20120109153758.GC9329@kroah.com> References: <1326099367-4166-1-git-send-email-youquan.song@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1326099367-4166-1-git-send-email-youquan.song@intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 09, 2012 at 04:56:07PM +0800, Youquan Song wrote: > sched_smt_power_savings is totally broken at lastest linux and -tip tree. > > sched_smt_power_savings is set to 1, the scheduler tries to schedule processes > on the least number of hyper-threads on a core as possible. In other words, > the process load is distributed such that all the hyper-threads in a core and > all the cores within the same processor are busy before the load is distributed > to other hyper-threads and cores in another processor. > > Test On Intel Xeon machine with 2 physical CPUs and each CPU has 8 cores / 16 > threads. physical CPU 0 includes cpu[0~7] and cpu[16~23]; while physical CPU 1 > includes cpu[8~15] and cpu[24~31]. > > At latest -tip tree: > echo 1 > /sys/devices/system/cpu/sched_smt_power_savings > ./ebizzy -t 16 -S 100 & sleep 10 ; cat /proc/sched_debug | grep -A 1 cpu# > tmp.log > > cpu#0, 2693.564 MHz > .nr_running : 0 > -- > cpu#1, 2693.564 MHz > .nr_running : 1 > -- > cpu#2, 2693.564 MHz > .nr_running : 0 > -- > cpu#3, 2693.564 MHz > .nr_running : 1 > -- > cpu#4, 2693.564 MHz > .nr_running : 1 > -- > cpu#5, 2693.564 MHz > .nr_running : 1 > -- > cpu#6, 2693.564 MHz > .nr_running : 1 > -- > cpu#7, 2693.564 MHz > .nr_running : 1 > -- > cpu#8, 2693.564 MHz > .nr_running : 1 > -- > cpu#9, 2693.564 MHz > .nr_running : 1 > -- > cpu#10, 2693.564 MHz > .nr_running : 1 > -- > cpu#11, 2693.564 MHz > .nr_running : 0 > -- > cpu#12, 2693.564 MHz > .nr_running : 1 > -- > cpu#13, 2693.564 MHz > .nr_running : 1 > -- > cpu#14, 2693.564 MHz > .nr_running : 0 > -- > cpu#15, 2693.564 MHz > .nr_running : 0 > -- > cpu#16, 2693.564 MHz > .nr_running : 0 > -- > cpu#17, 2693.564 MHz > .nr_running : 0 > -- > cpu#18, 2693.564 MHz > .nr_running : 1 > -- > cpu#19, 2693.564 MHz > .nr_running : 0 > -- > cpu#20, 2693.564 MHz > .nr_running : 0 > -- > cpu#21, 2693.564 MHz > .nr_running : 0 > -- > cpu#22, 2693.564 MHz > .nr_running : 0 > -- > cpu#23, 2693.564 MHz > .nr_running : 0 > -- > cpu#24, 2693.564 MHz > .nr_running : 0 > -- > cpu#25, 2693.564 MHz > .nr_running : 1 > -- > cpu#26, 2693.564 MHz > .nr_running : 1 > -- > cpu#27, 2693.564 MHz > .nr_running : 1 > -- > cpu#28, 2693.564 MHz > .nr_running : 0 > -- > cpu#29, 2693.564 MHz > .nr_running : 0 > -- > cpu#30, 2693.564 MHz > .nr_running : 1 > -- > cpu#31, 2693.564 MHz > .nr_running : 1 > > >From above, we notice 16 threads are distributed among 2 physical CPUs. > After apply the patch, 16 threads are only distributed at one physical CPU. > In this case, we can notice 30% power saving. > Following are the result after apply the patch: > > cpu#0, 2693.384 MHz > .nr_running : 1 > -- > cpu#1, 2693.384 MHz > .nr_running : 1 > -- > cpu#2, 2693.384 MHz > .nr_running : 1 > -- > cpu#3, 2693.384 MHz > .nr_running : 1 > -- > cpu#4, 2693.384 MHz > .nr_running : 1 > -- > cpu#5, 2693.384 MHz > .nr_running : 1 > -- > cpu#6, 2693.384 MHz > .nr_running : 1 > -- > cpu#7, 2693.384 MHz > .nr_running : 1 > -- > cpu#8, 2693.384 MHz > .nr_running : 0 > -- > cpu#9, 2693.384 MHz > .nr_running : 0 > -- > cpu#10, 2693.384 MHz > .nr_running : 0 > -- > cpu#11, 2693.384 MHz > .nr_running : 0 > -- > cpu#12, 2693.384 MHz > .nr_running : 0 > -- > cpu#13, 2693.384 MHz > .nr_running : 0 > -- > cpu#14, 2693.384 MHz > .nr_running : 0 > -- > cpu#15, 2693.384 MHz > .nr_running : 0 > -- > cpu#16, 2693.384 MHz > .nr_running : 1 > -- > cpu#17, 2693.384 MHz > .nr_running : 1 > -- > cpu#18, 2693.384 MHz > .nr_running : 1 > -- > cpu#19, 2693.384 MHz > .nr_running : 1 > -- > cpu#20, 2693.384 MHz > .nr_running : 1 > -- > cpu#21, 2693.384 MHz > .nr_running : 1 > -- > cpu#22, 2693.384 MHz > .nr_running : 1 > -- > cpu#23, 2693.384 MHz > .nr_running : 1 > -- > cpu#24, 2693.384 MHz > .nr_running : 0 > -- > cpu#25, 2693.384 MHz > .nr_running : 0 > -- > cpu#26, 2693.384 MHz > .nr_running : 0 > -- > cpu#27, 2693.384 MHz > .nr_running : 0 > -- > cpu#28, 2693.384 MHz > .nr_running : 0 > -- > cpu#29, 2693.384 MHz > .nr_running : 0 > -- > cpu#30, 2693.384 MHz > .nr_running : 0 > -- > cpu#31, 2693.384 MHz > .nr_running : 1 > > > This patch will set SMT sibling power capability to SCHED_POWER_SCALE > (1024) when sched_smt_power_savings set. So when there is possible do power > saving during scheduling, scheduler will truly schedule processes as > sched_smt_power_savings should do. > > > Signed-off-by: Youquan Song > Tested-by: Anhua Xu > --- > kernel/sched/fair.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read Documentation/stable_kernel_rules.txt for how to do this properly.