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Mon, 10 Mar 2025 10:05:04 -0700 (PDT) From: =?UTF-8?q?Michal=20Koutn=C3=BD?= To: Peter Zijlstra , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Frederic Weisbecker , =?UTF-8?q?Michal=20Koutn=C3=BD?= Subject: [PATCH v2 07/10] sched: Do not construct nor expose RT_GROUP_SCHED structures if disabled Date: Mon, 10 Mar 2025 18:04:39 +0100 Message-ID: <20250310170442.504716-8-mkoutny@suse.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250310170442.504716-1-mkoutny@suse.com> References: <20250310170442.504716-1-mkoutny@suse.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Thanks to kernel cmdline being available early, before any cgroup hierarchy exists, we can achieve the RT_GROUP_SCHED boottime disabling goal by simply skipping any creation (and destruction) of RT_GROUP data and its exposure via RT attributes. We can do this thanks to previously placed runtime guards that would redirect all operations to root_task_group's data when RT_GROUP_SCHED disabled. Signed-off-by: Michal Koutn=C3=BD --- kernel/sched/core.c | 36 ++++++++++++++++++++++++------------ kernel/sched/rt.c | 9 +++++++++ 2 files changed, 33 insertions(+), 12 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a418e7bc6a123..4b2d9ec0c1f23 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -9827,18 +9827,6 @@ static struct cftype cpu_legacy_files[] =3D { .seq_show =3D cpu_cfs_local_stat_show, }, #endif -#ifdef CONFIG_RT_GROUP_SCHED - { - .name =3D "rt_runtime_us", - .read_s64 =3D cpu_rt_runtime_read, - .write_s64 =3D cpu_rt_runtime_write, - }, - { - .name =3D "rt_period_us", - .read_u64 =3D cpu_rt_period_read_uint, - .write_u64 =3D cpu_rt_period_write_uint, - }, -#endif #ifdef CONFIG_UCLAMP_TASK_GROUP { .name =3D "uclamp.min", @@ -9857,6 +9845,20 @@ static struct cftype cpu_legacy_files[] =3D { }; =20 #ifdef CONFIG_RT_GROUP_SCHED +static struct cftype rt_group_files[] =3D { + { + .name =3D "rt_runtime_us", + .read_s64 =3D cpu_rt_runtime_read, + .write_s64 =3D cpu_rt_runtime_write, + }, + { + .name =3D "rt_period_us", + .read_u64 =3D cpu_rt_period_read_uint, + .write_u64 =3D cpu_rt_period_write_uint, + }, + { } /* Terminate */ +}; + # ifdef CONFIG_RT_GROUP_SCHED_DEFAULT_DISABLED DEFINE_STATIC_KEY_FALSE(rt_group_sched); # else @@ -9879,6 +9881,16 @@ static int __init setup_rt_group_sched(char *str) return 1; } __setup("rt_group_sched=3D", setup_rt_group_sched); + +static int __init cpu_rt_group_init(void) +{ + if (!rt_group_sched_enabled()) + return 0; + + WARN_ON(cgroup_add_legacy_cftypes(&cpu_cgrp_subsys, rt_group_files)); + return 0; +} +subsys_initcall(cpu_rt_group_init); #endif /* CONFIG_RT_GROUP_SCHED */ =20 static int cpu_extra_stat_show(struct seq_file *sf, diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index f25fe2862a7df..1633b49b2ce26 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -195,6 +195,9 @@ static inline struct rq *rq_of_rt_se(struct sched_rt_en= tity *rt_se) =20 void unregister_rt_sched_group(struct task_group *tg) { + if (!rt_group_sched_enabled()) + return; + if (tg->rt_se) destroy_rt_bandwidth(&tg->rt_bandwidth); } @@ -203,6 +206,9 @@ void free_rt_sched_group(struct task_group *tg) { int i; =20 + if (!rt_group_sched_enabled()) + return; + for_each_possible_cpu(i) { if (tg->rt_rq) kfree(tg->rt_rq[i]); @@ -247,6 +253,9 @@ int alloc_rt_sched_group(struct task_group *tg, struct = task_group *parent) struct sched_rt_entity *rt_se; int i; =20 + if (!rt_group_sched_enabled()) + return 1; + tg->rt_rq =3D kcalloc(nr_cpu_ids, sizeof(rt_rq), GFP_KERNEL); if (!tg->rt_rq) goto err; --=20 2.48.1