sched_ext: Add support for cgroup bandwidth control interface

From 077814f57f8acce13f91dc34bbd2b7e4911fbf25 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Fri, 13 Jun 2025 15:06:47 -1000

- Add CONFIG_GROUP_SCHED_BANDWIDTH which is selected by both
  CONFIG_CFS_BANDWIDTH and EXT_GROUP_SCHED.

- Put bandwidth control interface files for both cgroup v1 and v2 under
  CONFIG_GROUP_SCHED_BANDWIDTH.

- Update tg_bandwidth() to fetch configuration parameters from fair if
  CONFIG_CFS_BANDWIDTH, SCX otherwise.

- Update tg_set_bandwidth() to update the parameters for both fair and SCX.

- Add bandwidth control parameters to struct scx_cgroup_init_args.

- Add sched_ext_ops.cgroup_set_bandwidth() which is invoked on bandwidth
  control parameter updates.

- Update scx_qmap and maximal selftest to test the new feature.

Signed-off-by: Tejun Heo <tj@kernel.org>

2 files changed, 28 insertions, 0 deletions

diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
index c3cd9a17d48e..69d877501cb7 100644
--- a/tools/sched_ext/scx_qmap.bpf.c
+++ b/tools/sched_ext/scx_qmap.bpf.c
@@ -615,6 +615,26 @@ void BPF_STRUCT_OPS(qmap_dump_task, struct scx_dump_ctx *dctx, struct task_struc
 		     taskc->force_local, taskc->core_sched_seq);
 }
 
+s32 BPF_STRUCT_OPS(qmap_cgroup_init, struct cgroup *cgrp, struct scx_cgroup_init_args *args)
+{
+	bpf_printk("CGRP INIT %llu weight=%u period=%lu quota=%ld burst=%lu",
+		   cgrp->kn->id, args->weight, args->bw_period_us,
+		   args->bw_quota_us, args->bw_burst_us);
+	return 0;
+}
+
+void BPF_STRUCT_OPS(qmap_cgroup_set_weight, struct cgroup *cgrp, u32 weight)
+{
+	bpf_printk("CGRP SET %llu weight=%u", cgrp->kn->id, weight);
+}
+
+void BPF_STRUCT_OPS(qmap_cgroup_set_bandwidth, struct cgroup *cgrp,
+		    u64 period_us, u64 quota_us, u64 burst_us)
+{
+	bpf_printk("CGRP SET %llu period=%lu quota=%ld burst=%lu", cgrp->kn->id,
+		   period_us, quota_us, burst_us);
+}
+
 /*
  * Print out the online and possible CPU map using bpf_printk() as a
  * demonstration of using the cpumask kfuncs and ops.cpu_on/offline().
@@ -840,6 +860,9 @@ SCX_OPS_DEFINE(qmap_ops,
 	       .dump			= (void *)qmap_dump,
 	       .dump_cpu		= (void *)qmap_dump_cpu,
 	       .dump_task		= (void *)qmap_dump_task,
+	       .cgroup_init		= (void *)qmap_cgroup_init,
+	       .cgroup_set_weight	= (void *)qmap_cgroup_set_weight,
+	       .cgroup_set_bandwidth	= (void *)qmap_cgroup_set_bandwidth,
 	       .cpu_online		= (void *)qmap_cpu_online,
 	       .cpu_offline		= (void *)qmap_cpu_offline,
 	       .init			= (void *)qmap_init,
diff --git a/tools/testing/selftests/sched_ext/maximal.bpf.c b/tools/testing/selftests/sched_ext/maximal.bpf.c
index 430f5e13bf55..01cf4f3da4e0 100644
--- a/tools/testing/selftests/sched_ext/maximal.bpf.c
+++ b/tools/testing/selftests/sched_ext/maximal.bpf.c
@@ -123,6 +123,10 @@ void BPF_STRUCT_OPS(maximal_cgroup_cancel_move, struct task_struct *p,
 void BPF_STRUCT_OPS(maximal_cgroup_set_weight, struct cgroup *cgrp, u32 weight)
 {}
 
+void BPF_STRUCT_OPS(maximal_cgroup_set_bandwidth, struct cgroup *cgrp,
+		    u64 period_us, u64 quota_us, u64 burst_us)
+{}
+
 s32 BPF_STRUCT_OPS_SLEEPABLE(maximal_init)
 {
 	return scx_bpf_create_dsq(DSQ_ID, -1);
@@ -160,6 +164,7 @@ struct sched_ext_ops maximal_ops = {
 	.cgroup_move		= (void *) maximal_cgroup_move,
 	.cgroup_cancel_move	= (void *) maximal_cgroup_cancel_move,
 	.cgroup_set_weight	= (void *) maximal_cgroup_set_weight,
+	.cgroup_set_bandwidth	= (void *) maximal_cgroup_set_bandwidth,
 	.init			= (void *) maximal_init,
 	.exit			= (void *) maximal_exit,
 	.name			= "maximal",