From patchwork Wed Nov 2 03:53:01 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Zhang X-Patchwork-Id: 13027711 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F947C4332F for ; Wed, 2 Nov 2022 03:54:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230027AbiKBDyC (ORCPT ); Tue, 1 Nov 2022 23:54:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41540 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229516AbiKBDyA (ORCPT ); Tue, 1 Nov 2022 23:54:00 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B5F6A2BDF; Tue, 1 Nov 2022 20:53:58 -0700 (PDT) Received: from dggpemm500020.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4N2CYR5wnKzRnsP; Wed, 2 Nov 2022 11:48:59 +0800 (CST) Received: from dggpemm500014.china.huawei.com (7.185.36.153) by dggpemm500020.china.huawei.com (7.185.36.49) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 2 Nov 2022 11:53:57 +0800 Received: from huawei.com (7.220.126.23) by dggpemm500014.china.huawei.com (7.185.36.153) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 2 Nov 2022 11:53:56 +0800 From: Song Zhang To: , , , , , , CC: , , , , , , , , Song Zhang Subject: [PATCH] sched/fair: Introduce priority load balance for CFS Date: Wed, 2 Nov 2022 11:53:01 +0800 Message-ID: <20221102035301.512892-1-zhangsong34@huawei.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 X-Originating-IP: [7.220.126.23] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add a new sysctl interface: /proc/sys/kernel/sched_prio_load_balance_enabled 0: default behavior 1: enable priority load balance for CFS For co-location with idle and non-idle tasks, when CFS do load balance, it is reasonable to prefer migrating non-idle tasks and migrating idle tasks lastly. This will reduce the interference by SCHED_IDLE tasks as much as possible. Testcase: - Spawn large number of idle(SCHED_IDLE) tasks occupy CPUs - Let non-idle tasks compete with idle tasks for CPU time. Using schbench to test non-idle tasks latency: $ ./schbench -m 1 -t 10 -r 30 -R 200 Test result: 1.Default behavior Latency percentiles (usec) runtime 30 (s) (4562 total samples) 50.0th: 62528 (2281 samples) 75.0th: 623616 (1141 samples) 90.0th: 764928 (687 samples) 95.0th: 824320 (225 samples) *99.0th: 920576 (183 samples) 99.5th: 953344 (23 samples) 99.9th: 1008640 (18 samples) min=9, max=1074466 2.Enable priority load balance Latency percentiles (usec) runtime 30 (s) (4391 total samples) 50.0th: 22624 (2204 samples) 75.0th: 48832 (1092 samples) 90.0th: 85376 (657 samples) 95.0th: 113280 (220 samples) *99.0th: 182528 (175 samples) 99.5th: 206592 (22 samples) 99.9th: 290304 (17 samples) min=6, max=351815 From percentile details, we see the benefit of priority load balance that 95% of non-idle tasks latencies stays no more than 113ms, while non-idle tasks latencies has got almost 50% over 600ms if priority load balance not enabled. Signed-off-by: Song Zhang --- include/linux/sched/sysctl.h | 4 +++ init/Kconfig | 10 ++++++ kernel/sched/core.c | 3 ++ kernel/sched/fair.c | 61 +++++++++++++++++++++++++++++++++++- kernel/sched/sched.h | 3 ++ kernel/sysctl.c | 11 +++++++ 6 files changed, 91 insertions(+), 1 deletion(-) diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index 303ee7dd0c7e..9b3673269ecc 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -32,6 +32,10 @@ extern unsigned int sysctl_numa_balancing_promote_rate_limit; #define sysctl_numa_balancing_mode 0 #endif +#ifdef CONFIG_SCHED_PRIO_LB +extern unsigned int sysctl_sched_prio_load_balance_enabled; +#endif + int sysctl_numa_balancing(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos); diff --git a/init/Kconfig b/init/Kconfig index 694f7c160c9c..b0dfe6701218 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1026,6 +1026,16 @@ config CFS_BANDWIDTH restriction. See Documentation/scheduler/sched-bwc.rst for more information. +config SCHED_PRIO_LB + bool "Priority load balance for CFS" + depends on SMP + default n + help + This feature enable CFS priority load balance to reduce + non-idle tasks latency interferenced by SCHED_IDLE tasks. + It prefer migrating non-idle tasks firstly and + migrating SCHED_IDLE tasks lastly. + config RT_GROUP_SCHED bool "Group scheduling for SCHED_RR/FIFO" depends on CGROUP_SCHED diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5800b0623ff3..9be35431fdd5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -9731,6 +9731,9 @@ void __init sched_init(void) rq->max_idle_balance_cost = sysctl_sched_migration_cost; INIT_LIST_HEAD(&rq->cfs_tasks); +#ifdef CONFIG_SCHED_PRIO_LB + INIT_LIST_HEAD(&rq->cfs_idle_tasks); +#endif rq_attach_root(rq, &def_root_domain); #ifdef CONFIG_NO_HZ_COMMON diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e4a0b8bd941c..bdeb04324f0c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -139,6 +139,10 @@ static int __init setup_sched_thermal_decay_shift(char *str) } __setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift); +#ifdef CONFIG_SCHED_PRIO_LB +unsigned int sysctl_sched_prio_load_balance_enabled; +#endif + #ifdef CONFIG_SMP /* * For asym packing, by default the lower numbered CPU has higher priority. @@ -3199,6 +3203,21 @@ static inline void update_scan_period(struct task_struct *p, int new_cpu) #endif /* CONFIG_NUMA_BALANCING */ +#ifdef CONFIG_SCHED_PRIO_LB +static void +adjust_rq_cfs_tasks( + void (*list_op)(struct list_head *, struct list_head *), + struct rq *rq, + struct sched_entity *se) +{ + if (sysctl_sched_prio_load_balance_enabled && + task_has_idle_policy(task_of(se))) + (*list_op)(&se->group_node, &rq->cfs_idle_tasks); + else + (*list_op)(&se->group_node, &rq->cfs_tasks); +} +#endif + static void account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) { @@ -3208,7 +3227,11 @@ account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) struct rq *rq = rq_of(cfs_rq); account_numa_enqueue(rq, task_of(se)); +#ifdef CONFIG_SCHED_PRIO_LB + adjust_rq_cfs_tasks(list_add, rq, se); +#else list_add(&se->group_node, &rq->cfs_tasks); +#endif } #endif cfs_rq->nr_running++; @@ -7631,7 +7654,11 @@ done: __maybe_unused; * the list, so our cfs_tasks list becomes MRU * one. */ +#ifdef CONFIG_SCHED_PRIO_LB + adjust_rq_cfs_tasks(list_move, rq, &p->se); +#else list_move(&p->se.group_node, &rq->cfs_tasks); +#endif #endif if (hrtick_enabled_fair(rq)) @@ -8156,11 +8183,18 @@ static void detach_task(struct task_struct *p, struct lb_env *env) static struct task_struct *detach_one_task(struct lb_env *env) { struct task_struct *p; + struct list_head *tasks = &env->src_rq->cfs_tasks; +#ifdef CONFIG_SCHED_PRIO_LB + bool has_detach_idle_tasks = false; +#endif lockdep_assert_rq_held(env->src_rq); +#ifdef CONFIG_SCHED_PRIO_LB +again: +#endif list_for_each_entry_reverse(p, - &env->src_rq->cfs_tasks, se.group_node) { + tasks, se.group_node) { if (!can_migrate_task(p, env)) continue; @@ -8175,6 +8209,13 @@ static struct task_struct *detach_one_task(struct lb_env *env) schedstat_inc(env->sd->lb_gained[env->idle]); return p; } +#ifdef CONFIG_SCHED_PRIO_LB + if (sysctl_sched_prio_load_balance_enabled && !has_detach_idle_tasks) { + has_detach_idle_tasks = true; + tasks = &env->src_rq->cfs_idle_tasks; + goto again; + } +#endif return NULL; } @@ -8190,6 +8231,9 @@ static int detach_tasks(struct lb_env *env) unsigned long util, load; struct task_struct *p; int detached = 0; +#ifdef CONFIG_SCHED_PRIO_LB + bool has_detach_idle_tasks = false; +#endif lockdep_assert_rq_held(env->src_rq); @@ -8205,6 +8249,9 @@ static int detach_tasks(struct lb_env *env) if (env->imbalance <= 0) return 0; +#ifdef CONFIG_SCHED_PRIO_LB +again: +#endif while (!list_empty(tasks)) { /* * We don't want to steal all, otherwise we may be treated likewise, @@ -8310,6 +8357,14 @@ static int detach_tasks(struct lb_env *env) list_move(&p->se.group_node, tasks); } +#ifdef CONFIG_SCHED_PRIO_LB + if (sysctl_sched_prio_load_balance_enabled && + !has_detach_idle_tasks && env->imbalance > 0) { + has_detach_idle_tasks = true; + tasks = &env->src_rq->cfs_idle_tasks; + goto again; + } +#endif /* * Right now, this is one of only two places we collect this stat * so we can safely collect detach_one_task() stats here rather @@ -11814,7 +11869,11 @@ static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first) * Move the next running task to the front of the list, so our * cfs_tasks list becomes MRU one. */ +#ifdef CONFIG_SCHED_PRIO_LB + adjust_rq_cfs_tasks(list_move, rq, se); +#else list_move(&se->group_node, &rq->cfs_tasks); +#endif } #endif diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 1644242ecd11..1b831c05ba30 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1053,6 +1053,9 @@ struct rq { int online; struct list_head cfs_tasks; +#ifdef CONFIG_SCHED_PRIO_LB + struct list_head cfs_idle_tasks; +#endif struct sched_avg avg_rt; struct sched_avg avg_dl; diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 188c305aeb8b..5fc0f9ffb675 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -2090,6 +2090,17 @@ static struct ctl_table kern_table[] = { .extra1 = SYSCTL_ONE, .extra2 = SYSCTL_INT_MAX, }, +#endif +#ifdef CONFIG_SCHED_PRIO_LB + { + .procname = "sched_prio_load_balance_enabled", + .data = &sysctl_sched_prio_load_balance_enabled, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, #endif { } };