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Wed, 21 Jan 2026 12:34:09 -0800 (PST) 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 , Nilay Vaish , K Prateek Nayak , linux-kernel@vger.kernel.org, Zecheng Li , Zecheng Li Subject: [PATCH v8 1/3] sched/fair: Co-locate cfs_rq and sched_entity in cfs_tg_state Date: Wed, 21 Jan 2026 15:33:34 -0500 Message-ID: <20260121203402.1008441-2-zli94@ncsu.edu> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260121203402.1008441-1-zli94@ncsu.edu> References: <20260121203402.1008441-1-zli94@ncsu.edu> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Zecheng Li Improve data locality and reduce pointer chasing by allocating struct cfs_rq and struct sched_entity together for non-root task groups. This is achieved by introducing a new combined struct cfs_tg_state that holds both objects in a single allocation. This patch: - Introduces struct cfs_tg_state that embeds cfs_rq, sched_entity, and sched_statistics together in a single structure. - Updates __schedstats_from_se() in stats.h to use cfs_tg_state for accessing sched_statistics from a group sched_entity. - Modifies alloc_fair_sched_group() and free_fair_sched_group() to allocate and free the new struct as a single unit. - Modifies the per-CPU pointers in task_group->se and task_group->cfs_rq to point to the members in the new combined structure. Signed-off-by: Zecheng Li Signed-off-by: Zecheng Li --- kernel/sched/fair.c | 18 ++++++------------ kernel/sched/sched.h | 12 ++++++++++++ kernel/sched/stats.h | 9 +-------- 3 files changed, 19 insertions(+), 20 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 04993c763a06..eadf72b3835e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -13619,8 +13619,6 @@ void free_fair_sched_group(struct task_group *tg) for_each_possible_cpu(i) { if (tg->cfs_rq) kfree(tg->cfs_rq[i]); - if (tg->se) - kfree(tg->se[i]); } =20 kfree(tg->cfs_rq); @@ -13629,6 +13627,7 @@ void free_fair_sched_group(struct task_group *tg) =20 int alloc_fair_sched_group(struct task_group *tg, struct task_group *paren= t) { + struct cfs_tg_state *state; struct sched_entity *se; struct cfs_rq *cfs_rq; int i; @@ -13645,16 +13644,13 @@ int alloc_fair_sched_group(struct task_group *tg,= struct task_group *parent) init_cfs_bandwidth(tg_cfs_bandwidth(tg), tg_cfs_bandwidth(parent)); =20 for_each_possible_cpu(i) { - cfs_rq =3D kzalloc_node(sizeof(struct cfs_rq), - GFP_KERNEL, cpu_to_node(i)); - if (!cfs_rq) + state =3D kzalloc_node(sizeof(*state), + GFP_KERNEL, cpu_to_node(i)); + if (!state) goto err; =20 - se =3D kzalloc_node(sizeof(struct sched_entity_stats), - GFP_KERNEL, cpu_to_node(i)); - if (!se) - goto err_free_rq; - + cfs_rq =3D &state->cfs_rq; + se =3D &state->se; init_cfs_rq(cfs_rq); init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); init_entity_runnable_average(se); @@ -13662,8 +13658,6 @@ int alloc_fair_sched_group(struct task_group *tg, s= truct task_group *parent) =20 return 1; =20 -err_free_rq: - kfree(cfs_rq); err: return 0; } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 58c9d244f12b..50b37ed2f7d6 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2191,6 +2191,18 @@ static inline struct task_group *task_group(struct t= ask_struct *p) return p->sched_task_group; } =20 +#ifdef CONFIG_FAIR_GROUP_SCHED +/* + * Defined here to be available before stats.h is included, since + * stats.h has dependencies on things defined later in this file. + */ +struct cfs_tg_state { + struct cfs_rq cfs_rq; + struct sched_entity se; + struct sched_statistics stats; +} __no_randomize_layout; +#endif + /* Change a task's cfs_rq and parent entity if it moves across CPUs/groups= */ static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h index c903f1a42891..63b9a800a354 100644 --- a/kernel/sched/stats.h +++ b/kernel/sched/stats.h @@ -89,19 +89,12 @@ static inline void rq_sched_info_depart (struct rq *rq= , unsigned long long delt =20 #endif /* CONFIG_SCHEDSTATS */ =20 -#ifdef CONFIG_FAIR_GROUP_SCHED -struct sched_entity_stats { - struct sched_entity se; - struct sched_statistics stats; -} __no_randomize_layout; -#endif - static inline struct sched_statistics * __schedstats_from_se(struct sched_entity *se) { #ifdef CONFIG_FAIR_GROUP_SCHED if (!entity_is_task(se)) - return &container_of(se, struct sched_entity_stats, se)->stats; + return &container_of(se, struct cfs_tg_state, se)->stats; #endif return &task_of(se)->stats; } --=20 2.52.0