From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752286AbdANMtf (ORCPT ); Sat, 14 Jan 2017 07:49:35 -0500 Received: from terminus.zytor.com ([198.137.202.10]:52172 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752131AbdANMte (ORCPT ); Sat, 14 Jan 2017 07:49:34 -0500 Date: Sat, 14 Jan 2017 04:48:52 -0800 From: tip-bot for Dietmar Eggemann Message-ID: Cc: tglx@linutronix.de, dietmar.eggemann@arm.com, pjt@kernel.org, hpa@zytor.com, efault@gmx.de, samuel.thibault@ens-lyon.org, mingo@kernel.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, peterz@infradead.org Reply-To: peterz@infradead.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, efault@gmx.de, samuel.thibault@ens-lyon.org, mingo@kernel.org, hpa@zytor.com, tglx@linutronix.de, pjt@kernel.org, dietmar.eggemann@arm.com In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/fair: Explain why MIN_SHARES isn't scaled in calc_cfs_shares() Git-Commit-ID: b8fd8423697b9ec729c5bb91737faad84ae19985 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: b8fd8423697b9ec729c5bb91737faad84ae19985 Gitweb: http://git.kernel.org/tip/b8fd8423697b9ec729c5bb91737faad84ae19985 Author: Dietmar Eggemann AuthorDate: Wed, 11 Jan 2017 11:29:47 +0000 Committer: Ingo Molnar CommitDate: Sat, 14 Jan 2017 11:30:02 +0100 sched/fair: Explain why MIN_SHARES isn't scaled in calc_cfs_shares() Signed-off-by: Dietmar Eggemann Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul Turner Cc: Peter Zijlstra Cc: Samuel Thibault Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/e9a4d858-bcf3-36b9-e3a9-449953e34569@arm.com Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2b866a2..274c747 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2657,6 +2657,18 @@ static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) if (tg_weight) shares /= tg_weight; + /* + * MIN_SHARES has to be unscaled here to support per-CPU partitioning + * of a group with small tg->shares value. It is a floor value which is + * assigned as a minimum load.weight to the sched_entity representing + * the group on a CPU. + * + * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024 + * on an 8-core system with 8 tasks each runnable on one CPU shares has + * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In + * case no task is runnable on a CPU MIN_SHARES=2 should be returned + * instead of 0. + */ if (shares < MIN_SHARES) shares = MIN_SHARES; if (shares > tg->shares)