Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751479AbcCaEA0 (ORCPT ); Thu, 31 Mar 2016 00:00:26 -0400 Received: from mga09.intel.com ([134.134.136.24]:43861 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756001AbcCaEAE (ORCPT ); Thu, 31 Mar 2016 00:00:04 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,420,1455004800"; d="scan'208";a="76319915" From: Yuyang Du To: peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org Cc: bsegall@google.com, pjt@google.com, morten.rasmussen@arm.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, lizefan@huawei.com, umgwanakikbuti@gmail.com, Yuyang Du Subject: [PATCH RESEND v2 6/6] sched/fair: Remove unconditionally inactive code Date: Thu, 31 Mar 2016 04:16:55 +0800 Message-Id: <1459369015-28375-7-git-send-email-yuyang.du@intel.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1459369015-28375-1-git-send-email-yuyang.du@intel.com> References: <1459369015-28375-1-git-send-email-yuyang.du@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4888 Lines: 117 The increased load resolution (fixed point arithmetic range) is unconditionally deactivated with #if 0, so it is effectively broken. But the increased load range is still used somewhere (e.g., in Google), so we keep this feature. The reconciliation is we define CONFIG_CFS_INCREASE_LOAD_RANGE and it depends on FAIR_GROUP_SCHED and 64BIT and BROKEN. Suggested-by: Ingo Molnar Signed-off-by: Yuyang Du --- init/Kconfig | 16 +++++++++++++++ kernel/sched/sched.h | 55 +++++++++++++++++++++------------------------------- 2 files changed, 38 insertions(+), 33 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 2232080..d072c09 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1025,6 +1025,22 @@ config CFS_BANDWIDTH restriction. See tip/Documentation/scheduler/sched-bwc.txt for more information. +config CFS_INCREASE_LOAD_RANGE + bool "Increase kernel load range" + depends on 64BIT && BROKEN + default n + help + Increase resolution of nice-level calculations for 64-bit architectures. + The extra resolution improves shares distribution and load balancing of + low-weight task groups (eg. nice +19 on an autogroup), deeper taskgroup + hierarchies, especially on larger systems. This is not a user-visible change + and does not change the user-interface for setting shares/weights. + We increase resolution only if we have enough bits to allow this increased + resolution (i.e. BITS_PER_LONG > 32). The costs for increasing resolution + when BITS_PER_LONG <= 32 are pretty high and the returns do not justify the + increased costs. + Currently broken: it increases power usage under light load. + config RT_GROUP_SCHED bool "Group scheduling for SCHED_RR/FIFO" depends on CGROUP_SCHED diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index ebe16e3..1bb0d69 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -42,39 +42,6 @@ static inline void update_cpu_load_active(struct rq *this_rq) { } #define NS_TO_JIFFIES(TIME) ((unsigned long)(TIME) / (NSEC_PER_SEC / HZ)) /* - * Increase resolution of nice-level calculations for 64-bit architectures. - * The extra resolution improves shares distribution and load balancing of - * low-weight task groups (eg. nice +19 on an autogroup), deeper taskgroup - * hierarchies, especially on larger systems. This is not a user-visible change - * and does not change the user-interface for setting shares/weights. - * - * We increase resolution only if we have enough bits to allow this increased - * resolution (i.e. BITS_PER_LONG > 32). The costs for increasing resolution - * when BITS_PER_LONG <= 32 are pretty high and the returns do not justify the - * increased costs. - */ -#if 0 /* BITS_PER_LONG > 32 -- currently broken: it increases power usage under light load */ -# define NICE_0_LOAD_SHIFT (SCHED_FIXEDPOINT_SHIFT + SCHED_FIXEDPOINT_SHIFT) -# define user_to_kernel_load(w) ((w) << SCHED_FIXEDPOINT_SHIFT) -# define kernel_to_user_load(w) ((w) >> SCHED_FIXEDPOINT_SHIFT) -#else -# define NICE_0_LOAD_SHIFT (SCHED_FIXEDPOINT_SHIFT) -# define user_to_kernel_load(w) (w) -# define kernel_to_user_load(w) (w) -#endif - -/* - * Task weight (visible to user) and its load (invisible to user) have - * independent resolution, but they should be well calibrated. We use - * user_to_kernel_load() and kernel_to_user_load(w) to convert between - * them. The following must be true: - * - * user_to_kernel_load(sched_prio_to_weight[USER_PRIO(NICE_TO_PRIO(0))]) == NICE_0_LOAD - * kernel_to_user_load(NICE_0_LOAD) == sched_prio_to_weight[USER_PRIO(NICE_TO_PRIO(0))] - */ -#define NICE_0_LOAD (1L << NICE_0_LOAD_SHIFT) - -/* * Single value that decides SCHED_DEADLINE internal math precision. * 10 -> just above 1us * 9 -> just above 0.5us @@ -1150,6 +1117,28 @@ extern const int sched_prio_to_weight[40]; extern const u32 sched_prio_to_wmult[40]; /* + * Task weight (visible to user) and its load (invisible to user) have + * independent ranges, but they should be well calibrated. We use + * user_to_kernel_load() and kernel_to_user_load(w) to convert between + * them. + * + * The following must also be true: + * user_to_kernel_load(sched_prio_to_weight[USER_PRIO(NICE_TO_PRIO(0))]) == NICE_0_LOAD + * kernel_to_user_load(NICE_0_LOAD) == sched_prio_to_weight[USER_PRIO(NICE_TO_PRIO(0))] + */ +#ifdef CONFIG_CFS_INCREASE_LOAD_RANGE +#define NICE_0_LOAD_SHIFT (SCHED_FIXEDPOINT_SHIFT + SCHED_FIXEDPOINT_SHIFT) +#define user_to_kernel_load(w) (w << SCHED_FIXEDPOINT_SHIFT) +#define kernel_to_user_load(w) (w >> SCHED_FIXEDPOINT_SHIFT) +#else +#define NICE_0_LOAD_SHIFT (SCHED_FIXEDPOINT_SHIFT) +#define user_to_kernel_load(w) (w) +#define kernel_to_user_load(w) (w) +#endif + +#define NICE_0_LOAD (1UL << NICE_0_LOAD_SHIFT) + +/* * {de,en}queue flags: * * DEQUEUE_SLEEP - task is no longer runnable -- 2.1.4