From mboxrd@z Thu Jan 1 00:00:00 1970 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 3CBAFC19F2D for ; Wed, 10 Aug 2022 01:57:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230187AbiHJB5E (ORCPT ); Tue, 9 Aug 2022 21:57:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230184AbiHJB4u (ORCPT ); Tue, 9 Aug 2022 21:56:50 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17A0B7C184 for ; Tue, 9 Aug 2022 18:56:48 -0700 (PDT) Received: from dggpemm500021.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4M2Y0K3g6szmVdJ; Wed, 10 Aug 2022 09:54:41 +0800 (CST) Received: from dggpemm500014.china.huawei.com (7.185.36.153) by dggpemm500021.china.huawei.com (7.185.36.109) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 10 Aug 2022 09:56:45 +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 15.1.2375.24; Wed, 10 Aug 2022 09:56:44 +0800 From: zhangsong To: , , , CC: , , , , , , , zhangsong , "kernel test robot" Subject: [PATCH v2] sched/fair: Introduce priority load balance to reduce interference from IDLE tasks Date: Wed, 10 Aug 2022 09:56:36 +0800 Message-ID: <20220810015636.3865248-1-zhangsong34@huawei.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [7.220.126.23] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For co-location with NORMAL and IDLE tasks, when CFS trigger load balance, it is reasonable to prefer migrating NORMAL(Latency Sensitive) tasks from the busy src CPU to dst CPU, and migrating IDLE tasks lastly. This is very important for reducing interference from IDLE tasks. So the CFS load balance can be optimized to below: 1.`cfs_tasks` list of CPU rq is owned by NORMAL tasks. 2.`cfs_idle_tasks` list of CPU rq which is owned by IDLE tasks. 3.Prefer to migrate NORMAL tasks of cfs_tasks to dst CPU. 4.Lastly migrate IDLE tasks of cfs_idle_tasks to dst CPU. This was tested with the following reproduction: - small number of NORMAL tasks colocated with a large number of IDLE tasks With this patch, NORMAL tasks latency can be reduced about 5~10% compared with current. Signed-off-by: zhangsong Reported-by: kernel test robot --- V1->V2: - fix build test error --- kernel/sched/core.c | 1 + kernel/sched/fair.c | 45 ++++++++++++++++++++++++++++++++++++++++---- kernel/sched/sched.h | 1 + 3 files changed, 43 insertions(+), 4 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ee28253c9ac0..7325c6e552d8 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -9733,6 +9733,7 @@ void __init sched_init(void) rq->max_idle_balance_cost = sysctl_sched_migration_cost; INIT_LIST_HEAD(&rq->cfs_tasks); + INIT_LIST_HEAD(&rq->cfs_idle_tasks); 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 914096c5b1ae..b62bec5b1eb9 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3034,6 +3034,21 @@ static inline void update_scan_period(struct task_struct *p, int new_cpu) #endif /* CONFIG_NUMA_BALANCING */ +#ifdef CONFIG_SMP +static void +adjust_rq_cfs_tasks(void (*list_op)(struct list_head *, struct list_head *), + struct rq *rq, + struct sched_entity *se) +{ + struct cfs_rq *cfs_rq = cfs_rq_of(se); + + if (task_has_idle_policy(task_of(se)) || tg_is_idle(cfs_rq->tg)) + (*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) { @@ -3043,7 +3058,7 @@ 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)); - list_add(&se->group_node, &rq->cfs_tasks); + adjust_rq_cfs_tasks(list_add, rq, se); } #endif cfs_rq->nr_running++; @@ -7465,7 +7480,7 @@ done: __maybe_unused; * the list, so our cfs_tasks list becomes MRU * one. */ - list_move(&p->se.group_node, &rq->cfs_tasks); + adjust_rq_cfs_tasks(list_move, rq, &p->se); #endif if (hrtick_enabled_fair(rq)) @@ -7788,6 +7803,9 @@ static int task_hot(struct task_struct *p, struct lb_env *env) if (unlikely(task_has_idle_policy(p))) return 0; + if (tg_is_idle(cfs_rq_of(&p->se)->tg)) + return 0; + /* SMT siblings share cache */ if (env->sd->flags & SD_SHARE_CPUCAPACITY) return 0; @@ -7800,6 +7818,11 @@ static int task_hot(struct task_struct *p, struct lb_env *env) &p->se == cfs_rq_of(&p->se)->last)) return 1; + /* Preempt sched idle cpu do not consider migration cost */ + if (cpus_share_cache(env->src_cpu, env->dst_cpu) && + sched_idle_cpu(env->dst_cpu)) + return 0; + if (sysctl_sched_migration_cost == -1) return 1; @@ -7990,11 +8013,14 @@ 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; + int loop = 0; lockdep_assert_rq_held(env->src_rq); +again: 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; @@ -8009,6 +8035,10 @@ static struct task_struct *detach_one_task(struct lb_env *env) schedstat_inc(env->sd->lb_gained[env->idle]); return p; } + if (++loop == 1) { + tasks = &env->src_rq->cfs_idle_tasks; + goto again; + } return NULL; } @@ -8026,6 +8056,7 @@ static int detach_tasks(struct lb_env *env) unsigned long util, load; struct task_struct *p; int detached = 0; + int loop = 0; lockdep_assert_rq_held(env->src_rq); @@ -8041,6 +8072,7 @@ static int detach_tasks(struct lb_env *env) if (env->imbalance <= 0) return 0; +again: while (!list_empty(tasks)) { /* * We don't want to steal all, otherwise we may be treated likewise, @@ -8142,6 +8174,11 @@ static int detach_tasks(struct lb_env *env) list_move(&p->se.group_node, tasks); } + if (env->imbalance > 0 && ++loop == 1) { + tasks = &env->src_rq->cfs_idle_tasks; + goto again; + } + /* * Right now, this is one of only two places we collect this stat * so we can safely collect detach_one_task() stats here rather @@ -11643,7 +11680,7 @@ 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. */ - list_move(&se->group_node, &rq->cfs_tasks); + adjust_rq_cfs_tasks(list_move, rq, se); } #endif diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index e26688d387ae..accb4eea9769 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1068,6 +1068,7 @@ struct rq { int online; struct list_head cfs_tasks; + struct list_head cfs_idle_tasks; struct sched_avg avg_rt; struct sched_avg avg_dl; -- 2.27.0