From nobody Fri Dec 19 21:30:20 2025 Received: from mail-qv1-f73.google.com (mail-qv1-f73.google.com [209.85.219.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6056A1A256E for ; Fri, 7 Nov 2025 04:38:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762490296; cv=none; b=a4HOtDYzm6z++YOZvj20HMQnonJqigBkUoNsBb4SVHi5hpl6Tow5hJyMPTAa7mw90pLWA/1qEadt4HJO8H2giA5OsQFuBazNutdday5rYVKpf0FqhS/ynSTFXjQDqakVoCme6jhKtCv+ZnW6TAuVKD9tMxWT0gpAxrpXpn4FBhM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762490296; c=relaxed/simple; bh=5FSVN6t16HUTQUIrBQI90gbY5f9LW3PO/Osyuixyd/g=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=DhIjueQhLM6f0sDqzpc0SrlVbCtS8Ao012KsY8sBMJ5+kClKWgiun9s6u1PnY6RcnLDDA8DabZIKzKExcFoiqhKCpSeQ/qvzKcEfk21oV2cyXrJRsoTkYSH5uszHoQEnHcX93/mpP7nXxWAjSLP2zfPEZPpRn6wTZb/RBtNx/Cw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--zecheng.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=TCsXQHOa; arc=none smtp.client-ip=209.85.219.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--zecheng.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="TCsXQHOa" Received: by mail-qv1-f73.google.com with SMTP id 6a1803df08f44-8803f43073bso11364456d6.0 for ; Thu, 06 Nov 2025 20:38:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1762490293; x=1763095093; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=NBWFEtspIzrg97TaHeeXIiA08f/quVSUywNGx/mI/Pw=; b=TCsXQHOaMKNTBI9G05WgB4tslVihnBnD4buoJRiMEWSiIu2tvOtMppYSm4UWD6AAy8 u7pz7yg8bliuFUtIG4XyiSk8dqmSKjCE1kbj89Ns+Pq2bR4LgKDqtb9WDqYNg6aKTHSq 7SIq/obxiwt/S/rIW5U2NpRDBDX1ISZLOxJ9B0Cr4d5QLg8mcDhSD+TGlq+w86AletmU rdbznG0c6l1+Yf9bh4BFcOiw/eb5CeSHnEsAfEIPyQAjHfJFY+H9/jBSNBl9ye+MFsug 5m3h4KFzdPqN9Lqmk2AygB1CQTgRcRjHC0TAR1XaRA+dAg8Z7p/z2sDn52Oj/rrapwUf nnKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1762490293; x=1763095093; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=NBWFEtspIzrg97TaHeeXIiA08f/quVSUywNGx/mI/Pw=; b=nSWzI5FU7jpIa0vIi60m0sczcbau0dKbF/aDqT8aVWpkRgLIh/fMR/LCZThulCFHpC 5vdjIGM4bfFhnsSnCCRvduCzUfFAHF78XkwpJlsxczAjc/WELgypv2mWg76Wksf+MTdh UUZjAK+KCthViOoOvF0y/0Kjmzwy8ONsgm2eXQ9xAmjJX6bPuNq+rn58cCNdTgiYv8Cr 4eirnbRBi90qo0Jh6gvejPH+9mH/AEFNUfEqSLeZChaYLwDLb40YgQddnMcV/ov9GERH AhRWp+k+tbVFxuEjUpR3Gwpi72TfG3KFlhL0mLx0FZJU19t4z4QSjD60ykzScZ73tAmi Qhyg== X-Forwarded-Encrypted: i=1; AJvYcCU6YpWg2eKX4JGlb7wljekL2y4wtFCIGCUyQUS/kCG+m8c7W136yv+EPHx3IbXI7BHWvLmBN32OqxkHi6Q=@vger.kernel.org X-Gm-Message-State: AOJu0Yz4pEscXoqxladqh0jbV88mBRjfrh3HZlsUfzZ4vIv+UAuLrghS R08AKuIjdCLtO6buM+FybGV1pXBu8CPncjUU1ZBGNw/y81veqnHsAN7xrs4wq1eQz9+g7TG7pVo fM/fZroDfzA== X-Google-Smtp-Source: AGHT+IE3kMhQogVWInfOC9o2A17iW8RABljN9iQmNQ36igUtZH+jBCvHZZ0MiPoyZTkK1d8FkyMyeeFEnXxF X-Received: from qvc1.prod.google.com ([2002:a05:6214:8101:b0:880:4abb:71c2]) (user=zecheng job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6214:1313:b0:880:4eeb:3661 with SMTP id 6a1803df08f44-8817678f529mr27356246d6.63.1762490293150; Thu, 06 Nov 2025 20:38:13 -0800 (PST) Date: Fri, 7 Nov 2025 04:38:04 +0000 In-Reply-To: <20251107043807.1758889-1-zecheng@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251107043807.1758889-1-zecheng@google.com> X-Mailer: git-send-email 2.51.2.1041.gc1ab5b90ca-goog Message-ID: <20251107043807.1758889-3-zecheng@google.com> Subject: [PATCH v5 2/3] sched/fair: Remove task_group->se pointer array From: Zecheng Li To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot Cc: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Rik van Riel , Chris Mason , Madadi Vineeth Reddy , Xu Liu , Blake Jones , Josh Don , linux-kernel@vger.kernel.org, Zecheng Li Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Now that struct sched_entity is co-located with struct cfs_rq for non-root task groups, the task_group->se pointer array is redundant. The associated sched_entity can be loaded directly from the cfs_rq. This patch performs the access conversion with the helpers: - is_root_task_group(tg): checks if a task group is the root task group. It compares the task group's address with the global root_task_group variable. - tg_se(tg, cpu): retrieves the cfs_rq and returns the address of the co-located se. This function checks if tg is the root task group to ensure behaving the same of previous tg->se[cpu]. Replaces all accesses that use the tg->se[cpu] pointer array with calls to the new tg_se(tg, cpu) accessor. - cfs_rq_se(cfs_rq): simplifies access paths like cfs_rq->tg->se[...] to use the co-located sched_entity. This function also checks if tg is the root task group to ensure same behavior. Since tg_se is not in very hot code paths, and the branch is a register comparison with an immediate value (`&root_task_group`), the performance impact is expected to be negligible. Signed-off-by: Zecheng Li --- kernel/sched/core.c | 7 ++----- kernel/sched/debug.c | 2 +- kernel/sched/fair.c | 27 ++++++++++----------------- kernel/sched/sched.h | 29 ++++++++++++++++++++++++----- 4 files changed, 37 insertions(+), 28 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 67b5f2faab36..12ebe1b4c8ae 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8558,7 +8558,7 @@ void __init sched_init(void) wait_bit_init(); =20 #ifdef CONFIG_FAIR_GROUP_SCHED - ptr +=3D 2 * nr_cpu_ids * sizeof(void **); + ptr +=3D nr_cpu_ids * sizeof(void **); #endif #ifdef CONFIG_RT_GROUP_SCHED ptr +=3D 2 * nr_cpu_ids * sizeof(void **); @@ -8567,9 +8567,6 @@ void __init sched_init(void) ptr =3D (unsigned long)kzalloc(ptr, GFP_NOWAIT); =20 #ifdef CONFIG_FAIR_GROUP_SCHED - root_task_group.se =3D (struct sched_entity **)ptr; - ptr +=3D nr_cpu_ids * sizeof(void **); - root_task_group.cfs_rq =3D (struct cfs_rq **)ptr; ptr +=3D nr_cpu_ids * sizeof(void **); =20 @@ -9635,7 +9632,7 @@ static int cpu_cfs_stat_show(struct seq_file *sf, voi= d *v) int i; =20 for_each_possible_cpu(i) { - stats =3D __schedstats_from_se(tg->se[i]); + stats =3D __schedstats_from_se(tg_se(tg, i)); ws +=3D schedstat_val(stats->wait_sum); } =20 diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 02e16b70a790..16542596d4b0 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -644,7 +644,7 @@ void dirty_sched_domain_sysctl(int cpu) #ifdef CONFIG_FAIR_GROUP_SCHED static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task= _group *tg) { - struct sched_entity *se =3D tg->se[cpu]; + struct sched_entity *se =3D tg_se(tg, cpu); =20 #define P(F) SEQ_printf(m, " .%-30s: %lld\n", #F, (long long)F) #define P_SCHEDSTAT(F) SEQ_printf(m, " .%-30s: %lld\n", \ diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1676119e302b..f9fb07d73a03 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6021,7 +6021,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) { struct rq *rq =3D rq_of(cfs_rq); struct cfs_bandwidth *cfs_b =3D tg_cfs_bandwidth(cfs_rq->tg); - struct sched_entity *se =3D cfs_rq->tg->se[cpu_of(rq)]; + struct sched_entity *se; =20 /* * It's possible we are called with !runtime_remaining due to things @@ -6036,7 +6036,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) if (cfs_rq->runtime_enabled && cfs_rq->runtime_remaining <=3D 0) return; =20 - se =3D cfs_rq->tg->se[cpu_of(rq)]; + se =3D cfs_rq_se(cfs_rq); =20 cfs_rq->throttled =3D 0; =20 @@ -9788,7 +9788,6 @@ static bool __update_blocked_fair(struct rq *rq, bool= *done) { struct cfs_rq *cfs_rq, *pos; bool decayed =3D false; - int cpu =3D cpu_of(rq); =20 /* * Iterates the task_group tree in a bottom up fashion, see @@ -9808,7 +9807,7 @@ static bool __update_blocked_fair(struct rq *rq, bool= *done) } =20 /* Propagate pending load changes to the parent, if any: */ - se =3D cfs_rq->tg->se[cpu]; + se =3D cfs_rq_se(cfs_rq); if (se && !skip_blocked_update(se)) update_load_avg(cfs_rq_of(se), se, UPDATE_TG); =20 @@ -9834,8 +9833,7 @@ static bool __update_blocked_fair(struct rq *rq, bool= *done) */ static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) { - struct rq *rq =3D rq_of(cfs_rq); - struct sched_entity *se =3D cfs_rq->tg->se[cpu_of(rq)]; + struct sched_entity *se =3D cfs_rq_se(cfs_rq); unsigned long now =3D jiffies; unsigned long load; =20 @@ -13367,7 +13365,6 @@ void free_fair_sched_group(struct task_group *tg) } =20 kfree(tg->cfs_rq); - kfree(tg->se); } =20 int alloc_fair_sched_group(struct task_group *tg, struct task_group *paren= t) @@ -13380,9 +13377,6 @@ int alloc_fair_sched_group(struct task_group *tg, s= truct task_group *parent) tg->cfs_rq =3D kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL); if (!tg->cfs_rq) goto err; - tg->se =3D kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL); - if (!tg->se) - goto err; =20 tg->shares =3D NICE_0_LOAD; =20 @@ -13397,7 +13391,7 @@ int alloc_fair_sched_group(struct task_group *tg, s= truct task_group *parent) cfs_rq =3D &combined->cfs_rq; se =3D &combined->se; init_cfs_rq(cfs_rq); - init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); + init_tg_cfs_entry(tg, cfs_rq, se, i, tg_se(parent, i)); init_entity_runnable_average(se); } =20 @@ -13416,7 +13410,7 @@ void online_fair_sched_group(struct task_group *tg) =20 for_each_possible_cpu(i) { rq =3D cpu_rq(i); - se =3D tg->se[i]; + se =3D tg_se(tg, i); rq_lock_irq(rq, &rf); update_rq_clock(rq); attach_entity_cfs_rq(se); @@ -13433,7 +13427,7 @@ void unregister_fair_sched_group(struct task_group = *tg) =20 for_each_possible_cpu(cpu) { struct cfs_rq *cfs_rq =3D tg->cfs_rq[cpu]; - struct sched_entity *se =3D tg->se[cpu]; + struct sched_entity *se =3D tg_se(tg, cpu); struct rq *rq =3D cpu_rq(cpu); =20 if (se) { @@ -13470,7 +13464,6 @@ void init_tg_cfs_entry(struct task_group *tg, struc= t cfs_rq *cfs_rq, init_cfs_rq_runtime(cfs_rq); =20 tg->cfs_rq[cpu] =3D cfs_rq; - tg->se[cpu] =3D se; =20 /* se could be NULL for root_task_group */ if (!se) @@ -13501,7 +13494,7 @@ static int __sched_group_set_shares(struct task_gro= up *tg, unsigned long shares) /* * We can't change the weight of the root cgroup. */ - if (!tg->se[0]) + if (is_root_task_group(tg)) return -EINVAL; =20 shares =3D clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES)); @@ -13512,7 +13505,7 @@ static int __sched_group_set_shares(struct task_gro= up *tg, unsigned long shares) tg->shares =3D shares; for_each_possible_cpu(i) { struct rq *rq =3D cpu_rq(i); - struct sched_entity *se =3D tg->se[i]; + struct sched_entity *se =3D tg_se(tg, i); struct rq_flags rf; =20 /* Propagate contribution to hierarchy */ @@ -13563,7 +13556,7 @@ int sched_group_set_idle(struct task_group *tg, lon= g idle) =20 for_each_possible_cpu(i) { struct rq *rq =3D cpu_rq(i); - struct sched_entity *se =3D tg->se[i]; + struct sched_entity *se =3D tg_se(tg, i); struct cfs_rq *grp_cfs_rq =3D tg->cfs_rq[i]; bool was_idle =3D cfs_rq_is_idle(grp_cfs_rq); long idle_task_delta; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 8db53f4d4d06..1133910a13c2 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -476,8 +476,6 @@ struct task_group { #endif =20 #ifdef CONFIG_FAIR_GROUP_SCHED - /* schedulable entities of this group on each CPU */ - struct sched_entity **se; /* runqueue "owned" by this group on each CPU */ struct cfs_rq **cfs_rq; unsigned long shares; @@ -923,7 +921,8 @@ struct dl_rq { }; =20 #ifdef CONFIG_FAIR_GROUP_SCHED - +/* Check whether a task group is root tg */ +#define is_root_task_group(tg) ((tg) =3D=3D &root_task_group) /* An entity is a task if it doesn't "own" a runqueue */ #define entity_is_task(se) (!se->my_q) =20 @@ -1609,6 +1608,26 @@ static inline struct task_struct *task_of(struct sch= ed_entity *se) return container_of(se, struct task_struct, se); } =20 +static inline struct sched_entity *tg_se(struct task_group *tg, int cpu) +{ + if (is_root_task_group(tg)) + return NULL; + + struct cfs_rq_with_se *combined =3D + container_of(tg->cfs_rq[cpu], struct cfs_rq_with_se, cfs_rq); + return &combined->se; +} + +static inline struct sched_entity *cfs_rq_se(struct cfs_rq *cfs_rq) +{ + if (is_root_task_group(cfs_rq->tg)) + return NULL; + + struct cfs_rq_with_se *combined =3D + container_of(cfs_rq, struct cfs_rq_with_se, cfs_rq); + return &combined->se; +} + static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) { return p->se.cfs_rq; @@ -2182,8 +2201,8 @@ static inline void set_task_rq(struct task_struct *p,= unsigned int cpu) #ifdef CONFIG_FAIR_GROUP_SCHED set_task_rq_fair(&p->se, p->se.cfs_rq, tg->cfs_rq[cpu]); p->se.cfs_rq =3D tg->cfs_rq[cpu]; - p->se.parent =3D tg->se[cpu]; - p->se.depth =3D tg->se[cpu] ? tg->se[cpu]->depth + 1 : 0; + p->se.parent =3D tg_se(tg, cpu); + p->se.depth =3D p->se.parent ? p->se.parent->depth + 1 : 0; #endif =20 #ifdef CONFIG_RT_GROUP_SCHED --=20 2.51.2.1041.gc1ab5b90ca-goog