diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h
index b1c95fb11c8d..dc51304b6599 100644
--- a/include/linux/sched/ext.h
+++ b/include/linux/sched/ext.h
@@ -12,6 +12,8 @@
 #include <linux/rhashtable.h>
 #include <linux/llist.h>
 
+struct cgroup;
+
 enum scx_consts {
 	SCX_OPS_NAME_LEN	= 128,
 	SCX_EXIT_REASON_LEN	= 128,
@@ -109,14 +111,27 @@ enum scx_ops_flags {
 	 */
 	SCX_OPS_ENQ_EXITING	= 1LLU << 2,
 
+	/*
+	 * CPU cgroup knob enable flags
+	 */
+	SCX_OPS_CGROUP_KNOB_WEIGHT = 1LLU << 16,	/* cpu.weight */
+
 	SCX_OPS_ALL_FLAGS	= SCX_OPS_KEEP_BUILTIN_IDLE |
 				  SCX_OPS_ENQ_LAST |
-				  SCX_OPS_ENQ_EXITING,
+				  SCX_OPS_ENQ_EXITING |
+				  SCX_OPS_CGROUP_KNOB_WEIGHT,
 };
 
 /* argument container for ops.enable() and friends */
 struct scx_enable_args {
-	/* empty for now */
+	/* the cgroup the task is joining */
+	struct cgroup		*cgroup;
+};
+
+/* argument container for ops->cgroup_init() */
+struct scx_cgroup_init_args {
+	/* the weight of the cgroup [1..10000] */
+	u32			weight;
 };
 
 /**
@@ -341,7 +356,8 @@ struct sched_ext_ops {
 	 * @p: task to enable BPF scheduling for
 	 * @args: enable arguments, see the struct definition
 	 *
-	 * Enable @p for BPF scheduling. @p will start running soon.
+	 * Enable @p for BPF scheduling. @p is now in the cgroup specified for
+	 * the preceding prep_enable() and will start running soon.
 	 */
 	void (*enable)(struct task_struct *p, struct scx_enable_args *args);
 
@@ -365,6 +381,77 @@ struct sched_ext_ops {
 	 */
 	void (*disable)(struct task_struct *p);
 
+	/**
+	 * cgroup_init - Initialize a cgroup
+	 * @cgrp: cgroup being initialized
+	 * @args: init arguments, see the struct definition
+	 *
+	 * Either the BPF scheduler is being loaded or @cgrp created, initialize
+	 * @cgrp for sched_ext. This operation may block.
+	 *
+	 * Return 0 for success, -errno for failure. An error return while
+	 * loading will abort loading of the BPF scheduler. During cgroup
+	 * creation, it will abort the specific cgroup creation.
+	 */
+	s32 (*cgroup_init)(struct cgroup *cgrp,
+			   struct scx_cgroup_init_args *args);
+
+	/**
+	 * cgroup_exit - Exit a cgroup
+	 * @cgrp: cgroup being exited
+	 *
+	 * Either the BPF scheduler is being unloaded or @cgrp destroyed, exit
+	 * @cgrp for sched_ext. This operation my block.
+	 */
+	void (*cgroup_exit)(struct cgroup *cgrp);
+
+	/**
+	 * cgroup_prep_move - Prepare a task to be moved to a different cgroup
+	 * @p: task being moved
+	 * @from: cgroup @p is being moved from
+	 * @to: cgroup @p is being moved to
+	 *
+	 * Prepare @p for move from cgroup @from to @to. This operation may
+	 * block and can be used for allocations.
+	 *
+	 * Return 0 for success, -errno for failure. An error return aborts the
+	 * migration.
+	 */
+	s32 (*cgroup_prep_move)(struct task_struct *p,
+				struct cgroup *from, struct cgroup *to);
+
+	/**
+	 * cgroup_move - Commit cgroup move
+	 * @p: task being moved
+	 * @from: cgroup @p is being moved from
+	 * @to: cgroup @p is being moved to
+	 *
+	 * Commit the move. @p is dequeued during this operation.
+	 */
+	void (*cgroup_move)(struct task_struct *p,
+			    struct cgroup *from, struct cgroup *to);
+
+	/**
+	 * cgroup_cancel_move - Cancel cgroup move
+	 * @p: task whose cgroup move is being canceled
+	 * @from: cgroup @p was being moved from
+	 * @to: cgroup @p was being moved to
+	 *
+	 * @p was cgroup_prep_move()'d but failed before reaching cgroup_move().
+	 * Undo the preparation.
+	 */
+	void (*cgroup_cancel_move)(struct task_struct *p,
+				   struct cgroup *from, struct cgroup *to);
+
+	/**
+	 * cgroup_set_weight - A cgroup's weight is being changed
+	 * @cgrp: cgroup whose weight is being updated
+	 * @weight: new weight [1..10000]
+	 *
+	 * Update @tg's weight to @weight.
+	 */
+	void (*cgroup_set_weight)(struct cgroup *cgrp, u32 weight);
+
 	/*
 	 * All online ops must come before ops.init().
 	 */
@@ -481,6 +568,9 @@ struct sched_ext_entity {
 
 	/* cold fields */
 	struct list_head	tasks_node;
+#ifdef CONFIG_EXT_GROUP_SCHED
+	struct cgroup		*cgrp_moving_from;
+#endif
 };
 
 void sched_ext_free(struct task_struct *p);
diff --git a/init/Kconfig b/init/Kconfig
index abf65098f1b6..826624ec8925 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1037,6 +1037,11 @@ config RT_GROUP_SCHED
 	  realtime bandwidth for them.
 	  See Documentation/scheduler/sched-rt-group.rst for more information.
 
+config EXT_GROUP_SCHED
+	bool
+	depends on SCHED_CLASS_EXT && CGROUP_SCHED
+	default y
+
 endif #CGROUP_SCHED
 
 config UCLAMP_TASK_GROUP
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 89d2421809da..79560641a61f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9720,6 +9720,9 @@ void __init sched_init(void)
 		root_task_group.shares = ROOT_TASK_GROUP_LOAD;
 		init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
 #endif /* CONFIG_FAIR_GROUP_SCHED */
+#ifdef CONFIG_EXT_GROUP_SCHED
+		root_task_group.scx_weight = CGROUP_WEIGHT_DFL;
+#endif /* CONFIG_EXT_GROUP_SCHED */
 #ifdef CONFIG_RT_GROUP_SCHED
 		root_task_group.rt_se = (struct sched_rt_entity **)ptr;
 		ptr += nr_cpu_ids * sizeof(void **);
@@ -10175,6 +10178,7 @@ struct task_group *sched_create_group(struct task_group *parent)
 	if (!alloc_rt_sched_group(tg, parent))
 		goto err;
 
+	scx_group_set_weight(tg, CGROUP_WEIGHT_DFL);
 	alloc_uclamp_sched_group(tg, parent);
 
 	return tg;
@@ -10286,6 +10290,8 @@ void sched_move_task(struct task_struct *tsk, enum sched_move_task_reason reason
 		put_prev_task(rq, tsk);
 
 	sched_change_group(tsk);
+	if (reason == SCHED_MOVE_TASK_CGROUP)
+		scx_cgroup_move_task(tsk);
 
 	if (queued)
 		enqueue_task(rq, tsk, queue_flags);
@@ -10325,6 +10331,11 @@ static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
 {
 	struct task_group *tg = css_tg(css);
 	struct task_group *parent = css_tg(css->parent);
+	int ret;
+
+	ret = scx_tg_online(tg);
+	if (ret)
+		return ret;
 
 	if (parent)
 		sched_online_group(tg, parent);
@@ -10341,6 +10352,13 @@ static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
 	return 0;
 }
 
+static void cpu_cgroup_css_offline(struct cgroup_subsys_state *css)
+{
+	struct task_group *tg = css_tg(css);
+
+	scx_tg_offline(tg);
+}
+
 static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
 {
 	struct task_group *tg = css_tg(css);
@@ -10358,9 +10376,10 @@ static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
 	sched_unregister_group(tg);
 }
 
-#ifdef CONFIG_RT_GROUP_SCHED
+#if defined(CONFIG_RT_GROUP_SCHED) || defined(CONFIG_EXT_GROUP_SCHED)
 static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
 {
+#ifdef CONFIG_RT_GROUP_SCHED
 	struct task_struct *task;
 	struct cgroup_subsys_state *css;
 
@@ -10368,7 +10387,8 @@ static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
 		if (!sched_rt_can_attach(css_tg(css), task))
 			return -EINVAL;
 	}
-	return 0;
+#endif
+	return scx_cgroup_can_attach(tset);
 }
 #endif
 
@@ -10379,7 +10399,16 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset)
 
 	cgroup_taskset_for_each(task, css, tset)
 		sched_move_task(task, SCHED_MOVE_TASK_CGROUP);
+
+	scx_cgroup_finish_attach();
+}
+
+#ifdef CONFIG_EXT_GROUP_SCHED
+static void cpu_cgroup_cancel_attach(struct cgroup_taskset *tset)
+{
+	scx_cgroup_cancel_attach(tset);
 }
+#endif
 
 #ifdef CONFIG_UCLAMP_TASK_GROUP
 static void cpu_util_update_eff(struct cgroup_subsys_state *css)
@@ -10562,9 +10591,15 @@ static int cpu_uclamp_max_show(struct seq_file *sf, void *v)
 static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
 				struct cftype *cftype, u64 shareval)
 {
+	int ret;
+
 	if (shareval > scale_load_down(ULONG_MAX))
 		shareval = MAX_SHARES;
-	return sched_group_set_shares(css_tg(css), scale_load(shareval));
+	ret = sched_group_set_shares(css_tg(css), scale_load(shareval));
+	if (!ret)
+		scx_group_set_weight(css_tg(css),
+				     sched_weight_to_cgroup(shareval));
+	return ret;
 }
 
 static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
@@ -11028,11 +11063,15 @@ static int cpu_extra_stat_show(struct seq_file *sf,
 	return 0;
 }
 
-#ifdef CONFIG_FAIR_GROUP_SCHED
+#if defined(CONFIG_FAIR_GROUP_SCHED) || defined(CONFIG_EXT_GROUP_SCHED)
 
 static unsigned long tg_weight(struct task_group *tg)
 {
+#ifdef CONFIG_FAIR_GROUP_SCHED
 	return scale_load_down(tg->shares);
+#else
+	return sched_weight_from_cgroup(tg->cgrp_weight);
+#endif
 }
 
 static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
@@ -11045,13 +11084,17 @@ static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
 				struct cftype *cft, u64 cgrp_weight)
 {
 	unsigned long weight;
+	int ret;
 
 	if (cgrp_weight < CGROUP_WEIGHT_MIN || cgrp_weight > CGROUP_WEIGHT_MAX)
 		return -ERANGE;
 
 	weight = sched_weight_from_cgroup(cgrp_weight);
 
-	return sched_group_set_shares(css_tg(css), scale_load(weight));
+	ret = sched_group_set_shares(css_tg(css), scale_load(weight));
+	if (!ret)
+		scx_group_set_weight(css_tg(css), cgrp_weight);
+	return ret;
 }
 
 static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
@@ -11076,7 +11119,7 @@ static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
 				     struct cftype *cft, s64 nice)
 {
 	unsigned long weight;
-	int idx;
+	int idx, ret;
 
 	if (nice < MIN_NICE || nice > MAX_NICE)
 		return -ERANGE;
@@ -11085,7 +11128,11 @@ static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
 	idx = array_index_nospec(idx, 40);
 	weight = sched_prio_to_weight[idx];
 
-	return sched_group_set_shares(css_tg(css), scale_load(weight));
+	ret = sched_group_set_shares(css_tg(css), scale_load(weight));
+	if (!ret)
+		scx_group_set_weight(css_tg(css),
+				     sched_weight_to_cgroup(weight));
+	return ret;
 }
 #endif
 
@@ -11147,7 +11194,7 @@ static ssize_t cpu_max_write(struct kernfs_open_file *of,
 #endif
 
 struct cftype cpu_cftypes[CPU_CFTYPE_CNT + 1] = {
-#ifdef CONFIG_FAIR_GROUP_SCHED
+#if defined(CONFIG_FAIR_GROUP_SCHED) || defined(CONFIG_EXT_GROUP_SCHED)
 	[CPU_CFTYPE_WEIGHT] = {
 		.name = "weight",
 		.flags = CFTYPE_NOT_ON_ROOT,
@@ -11201,13 +11248,17 @@ struct cftype cpu_cftypes[CPU_CFTYPE_CNT + 1] = {
 struct cgroup_subsys cpu_cgrp_subsys = {
 	.css_alloc	= cpu_cgroup_css_alloc,
 	.css_online	= cpu_cgroup_css_online,
+	.css_offline	= cpu_cgroup_css_offline,
 	.css_released	= cpu_cgroup_css_released,
 	.css_free	= cpu_cgroup_css_free,
 	.css_extra_stat_show = cpu_extra_stat_show,
-#ifdef CONFIG_RT_GROUP_SCHED
+#if defined(CONFIG_RT_GROUP_SCHED) || defined(CONFIG_EXT_GROUP_SCHED)
 	.can_attach	= cpu_cgroup_can_attach,
 #endif
 	.attach		= cpu_cgroup_attach,
+#ifdef CONFIG_EXT_GROUP_SCHED
+	.cancel_attach	= cpu_cgroup_cancel_attach,
+#endif
 	.legacy_cftypes	= cpu_legacy_cftypes,
 	.dfl_cftypes	= cpu_cftypes,
 	.early_init	= true,
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index cf6493f684f3..bd03b55fbcf5 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -1561,6 +1561,19 @@ static void task_tick_scx(struct rq *rq, struct task_struct *curr, int queued)
 		resched_curr(rq);
 }
 
+static struct cgroup *tg_cgrp(struct task_group *tg)
+{
+	/*
+	 * If CGROUP_SCHED is disabled, @tg is NULL. If @tg is an autogroup,
+	 * @tg->css.cgroup is NULL. In both cases, @tg can be treated as the
+	 * root cgroup.
+	 */
+	if (tg && tg->css.cgroup)
+		return tg->css.cgroup;
+	else
+		return &cgrp_dfl_root.cgrp;
+}
+
 static int scx_ops_prepare_task(struct task_struct *p, struct task_group *tg)
 {
 	int ret;
@@ -1570,7 +1583,7 @@ static int scx_ops_prepare_task(struct task_struct *p, struct task_group *tg)
 	p->scx.disallow = false;
 
 	if (SCX_HAS_OP(prep_enable)) {
-		struct scx_enable_args args = { };
+		struct scx_enable_args args = { .cgroup = tg_cgrp(tg) };
 
 		ret = scx_ops.prep_enable(p, &args);
 		if (unlikely(ret)) {
@@ -1610,7 +1623,8 @@ static void scx_ops_enable_task(struct task_struct *p)
 	WARN_ON_ONCE(!(p->scx.flags & SCX_TASK_OPS_PREPPED));
 
 	if (SCX_HAS_OP(enable)) {
-		struct scx_enable_args args = { };
+		struct scx_enable_args args =
+			{ .cgroup = tg_cgrp(p->sched_task_group) };
 		scx_ops.enable(p, &args);
 	}
 	p->scx.flags &= ~SCX_TASK_OPS_PREPPED;
@@ -1623,7 +1637,8 @@ static void scx_ops_disable_task(struct task_struct *p)
 
 	if (p->scx.flags & SCX_TASK_OPS_PREPPED) {
 		if (SCX_HAS_OP(cancel_enable)) {
-			struct scx_enable_args args = { };
+			struct scx_enable_args args =
+				{ .cgroup = tg_cgrp(task_group(p)) };
 			scx_ops.cancel_enable(p, &args);
 		}
 		p->scx.flags &= ~SCX_TASK_OPS_PREPPED;
@@ -1777,6 +1792,156 @@ bool scx_can_stop_tick(struct rq *rq)
 }
 #endif
 
+#ifdef CONFIG_EXT_GROUP_SCHED
+
+DEFINE_STATIC_PERCPU_RWSEM(scx_cgroup_rwsem);
+
+int scx_tg_online(struct task_group *tg)
+{
+	int ret = 0;
+
+	WARN_ON_ONCE(tg->scx_flags & (SCX_TG_ONLINE | SCX_TG_INITED));
+
+	percpu_down_read(&scx_cgroup_rwsem);
+
+	if (SCX_HAS_OP(cgroup_init)) {
+		struct scx_cgroup_init_args args = { .weight = tg->scx_weight };
+
+		ret = scx_ops.cgroup_init(tg->css.cgroup, &args);
+		if (!ret)
+			tg->scx_flags |= SCX_TG_ONLINE | SCX_TG_INITED;
+		else
+			ret = ops_sanitize_err("cgroup_init", ret);
+	} else {
+		tg->scx_flags |= SCX_TG_ONLINE;
+	}
+
+	percpu_up_read(&scx_cgroup_rwsem);
+	return ret;
+}
+
+void scx_tg_offline(struct task_group *tg)
+{
+	WARN_ON_ONCE(!(tg->scx_flags & SCX_TG_ONLINE));
+
+	percpu_down_read(&scx_cgroup_rwsem);
+
+	if (SCX_HAS_OP(cgroup_exit) && (tg->scx_flags & SCX_TG_INITED))
+		scx_ops.cgroup_exit(tg->css.cgroup);
+	tg->scx_flags &= ~(SCX_TG_ONLINE | SCX_TG_INITED);
+
+	percpu_up_read(&scx_cgroup_rwsem);
+}
+
+int scx_cgroup_can_attach(struct cgroup_taskset *tset)
+{
+	struct cgroup_subsys_state *css;
+	struct task_struct *p;
+	int ret;
+
+	/* released in scx_finish/cancel_attach() */
+	percpu_down_read(&scx_cgroup_rwsem);
+
+	if (!scx_enabled())
+		return 0;
+
+	cgroup_taskset_for_each(p, css, tset) {
+		struct cgroup *from = tg_cgrp(p->sched_task_group);
+
+		if (SCX_HAS_OP(cgroup_prep_move)) {
+			ret = scx_ops.cgroup_prep_move(p, from, css->cgroup);
+			if (ret)
+				goto err;
+		}
+
+		WARN_ON_ONCE(p->scx.cgrp_moving_from);
+		p->scx.cgrp_moving_from = from;
+	}
+
+	return 0;
+
+err:
+	cgroup_taskset_for_each(p, css, tset) {
+		if (!p->scx.cgrp_moving_from)
+			break;
+		if (SCX_HAS_OP(cgroup_cancel_move))
+			scx_ops.cgroup_cancel_move(p, p->scx.cgrp_moving_from,
+						   css->cgroup);
+		p->scx.cgrp_moving_from = NULL;
+	}
+
+	percpu_up_read(&scx_cgroup_rwsem);
+	return ops_sanitize_err("cgroup_prep_move", ret);
+}
+
+void scx_cgroup_move_task(struct task_struct *p)
+{
+	if (!scx_enabled())
+		return;
+
+	if (SCX_HAS_OP(cgroup_move)) {
+		WARN_ON_ONCE(!p->scx.cgrp_moving_from);
+		scx_ops.cgroup_move(p, p->scx.cgrp_moving_from,
+				    tg_cgrp(p->sched_task_group));
+	}
+	p->scx.cgrp_moving_from = NULL;
+}
+
+void scx_cgroup_finish_attach(void)
+{
+	percpu_up_read(&scx_cgroup_rwsem);
+}
+
+void scx_cgroup_cancel_attach(struct cgroup_taskset *tset)
+{
+	struct cgroup_subsys_state *css;
+	struct task_struct *p;
+
+	if (!scx_enabled())
+		goto out_unlock;
+
+	cgroup_taskset_for_each(p, css, tset) {
+		if (SCX_HAS_OP(cgroup_cancel_move)) {
+			WARN_ON_ONCE(!p->scx.cgrp_moving_from);
+			scx_ops.cgroup_cancel_move(p, p->scx.cgrp_moving_from,
+						   css->cgroup);
+		}
+		p->scx.cgrp_moving_from = NULL;
+	}
+out_unlock:
+	percpu_up_read(&scx_cgroup_rwsem);
+}
+
+void scx_group_set_weight(struct task_group *tg, unsigned long weight)
+{
+	percpu_down_read(&scx_cgroup_rwsem);
+
+	if (tg->scx_weight != weight) {
+		if (SCX_HAS_OP(cgroup_set_weight))
+			scx_ops.cgroup_set_weight(tg_cgrp(tg), weight);
+		tg->scx_weight = weight;
+	}
+
+	percpu_up_read(&scx_cgroup_rwsem);
+}
+
+static void scx_cgroup_lock(void)
+{
+	percpu_down_write(&scx_cgroup_rwsem);
+}
+
+static void scx_cgroup_unlock(void)
+{
+	percpu_up_write(&scx_cgroup_rwsem);
+}
+
+#else	/* CONFIG_EXT_GROUP_SCHED */
+
+static inline void scx_cgroup_lock(void) {}
+static inline void scx_cgroup_unlock(void) {}
+
+#endif	/* CONFIG_EXT_GROUP_SCHED */
+
 /*
  * Omitted operations:
  *
@@ -1916,6 +2081,130 @@ static void destroy_dsq(u64 dsq_id)
 	rcu_read_unlock();
 }
 
+#ifdef CONFIG_EXT_GROUP_SCHED
+static void scx_cgroup_exit(void)
+{
+	struct cgroup_subsys_state *css;
+
+	percpu_rwsem_assert_held(&scx_cgroup_rwsem);
+
+	/*
+	 * scx_tg_on/offline() are excluded through scx_cgroup_rwsem. If we walk
+	 * cgroups and exit all the inited ones, all online cgroups are exited.
+	 */
+	rcu_read_lock();
+	css_for_each_descendant_post(css, &root_task_group.css) {
+		struct task_group *tg = css_tg(css);
+
+		if (!(tg->scx_flags & SCX_TG_INITED))
+			continue;
+		tg->scx_flags &= ~SCX_TG_INITED;
+
+		if (!scx_ops.cgroup_exit)
+			continue;
+
+		if (WARN_ON_ONCE(!css_tryget(css)))
+			continue;
+		rcu_read_unlock();
+
+		scx_ops.cgroup_exit(css->cgroup);
+
+		rcu_read_lock();
+		css_put(css);
+	}
+	rcu_read_unlock();
+}
+
+static int scx_cgroup_init(void)
+{
+	struct cgroup_subsys_state *css;
+	int ret;
+
+	percpu_rwsem_assert_held(&scx_cgroup_rwsem);
+
+	/*
+	 * scx_tg_on/offline() are excluded thorugh scx_cgroup_rwsem. If we walk
+	 * cgroups and init, all online cgroups are initialized.
+	 */
+	rcu_read_lock();
+	css_for_each_descendant_pre(css, &root_task_group.css) {
+		struct task_group *tg = css_tg(css);
+		struct scx_cgroup_init_args args = { .weight = tg->scx_weight };
+
+		if ((tg->scx_flags &
+		     (SCX_TG_ONLINE | SCX_TG_INITED)) != SCX_TG_ONLINE)
+			continue;
+
+		if (!scx_ops.cgroup_init) {
+			tg->scx_flags |= SCX_TG_INITED;
+			continue;
+		}
+
+		if (WARN_ON_ONCE(!css_tryget(css)))
+			continue;
+		rcu_read_unlock();
+
+		ret = scx_ops.cgroup_init(css->cgroup, &args);
+		if (ret) {
+			css_put(css);
+			return ret;
+		}
+		tg->scx_flags |= SCX_TG_INITED;
+
+		rcu_read_lock();
+		css_put(css);
+	}
+	rcu_read_unlock();
+
+	return 0;
+}
+
+static void scx_cgroup_config_knobs(void)
+{
+	static DEFINE_MUTEX(cgintf_mutex);
+	DECLARE_BITMAP(mask, CPU_CFTYPE_CNT) = { };
+	u64 knob_flags;
+	int i;
+
+	/*
+	 * Called from both class switch and ops enable/disable paths,
+	 * synchronize internally.
+	 */
+	mutex_lock(&cgintf_mutex);
+
+	/* if fair is in use, all knobs should be shown */
+	if (!scx_switched_all()) {
+		bitmap_fill(mask, CPU_CFTYPE_CNT);
+		goto apply;
+	}
+
+	/*
+	 * On ext, only show the supported knobs. Otherwise, show all possible
+	 * knobs so that configuration attempts succeed and the states are
+	 * remembered while ops is not loaded.
+	 */
+	if (scx_enabled())
+		knob_flags = scx_ops.flags;
+	else
+		knob_flags = SCX_OPS_ALL_FLAGS;
+
+	if (knob_flags & SCX_OPS_CGROUP_KNOB_WEIGHT) {
+		__set_bit(CPU_CFTYPE_WEIGHT, mask);
+		__set_bit(CPU_CFTYPE_WEIGHT_NICE, mask);
+	}
+apply:
+	for (i = 0; i < CPU_CFTYPE_CNT; i++)
+		cgroup_show_cftype(&cpu_cftypes[i], test_bit(i, mask));
+
+	mutex_unlock(&cgintf_mutex);
+}
+
+#else
+static void scx_cgroup_exit(void) {}
+static int scx_cgroup_init(void) { return 0; }
+static void scx_cgroup_config_knobs(void) {}
+#endif
+
 /*
  * Used by sched_fork() and __setscheduler_prio() to pick the matching
  * sched_class. dl/rt are already handled.
@@ -2071,9 +2360,10 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
 	static_branch_disable(&__scx_switched_all);
 	WRITE_ONCE(scx_switching_all, false);
 
-	/* avoid racing against fork */
+	/* avoid racing against fork and cgroup changes */
 	cpus_read_lock();
 	percpu_down_write(&scx_fork_rwsem);
+	scx_cgroup_lock();
 
 	spin_lock_irq(&scx_tasks_lock);
 	scx_task_iter_init(&sti);
@@ -2108,6 +2398,9 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
 	static_branch_disable_cpuslocked(&scx_builtin_idle_enabled);
 	synchronize_rcu();
 
+	scx_cgroup_exit();
+
+	scx_cgroup_unlock();
 	percpu_up_write(&scx_fork_rwsem);
 	cpus_read_unlock();
 
@@ -2137,6 +2430,8 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
 
 	WARN_ON_ONCE(scx_ops_set_enable_state(SCX_OPS_DISABLED) !=
 		     SCX_OPS_DISABLING);
+
+	scx_cgroup_config_knobs();
 }
 
 static DEFINE_KTHREAD_WORK(scx_ops_disable_work, scx_ops_disable_workfn);
@@ -2293,10 +2588,11 @@ static int scx_ops_enable(struct sched_ext_ops *ops)
 			   task_runnable_timeout_ms / 2);
 
 	/*
-	 * Lock out forks before opening the floodgate so that they don't wander
-	 * into the operations prematurely.
+	 * Lock out forks, cgroup on/offlining and moves before opening the
+	 * floodgate so that they don't wander into the operations prematurely.
 	 */
 	percpu_down_write(&scx_fork_rwsem);
+	scx_cgroup_lock();
 
 	for (i = 0; i < SCX_NR_ONLINE_OPS; i++)
 		if (((void (**)(void))ops)[i])
@@ -2315,6 +2611,14 @@ static int scx_ops_enable(struct sched_ext_ops *ops)
 		static_branch_disable_cpuslocked(&scx_builtin_idle_enabled);
 	}
 
+	/*
+	 * All cgroups should be initialized before letting in tasks. cgroup
+	 * on/offlining and task migrations are already locked out.
+	 */
+	ret = scx_cgroup_init();
+	if (ret)
+		goto err_disable_unlock;
+
 	static_branch_enable_cpuslocked(&__scx_ops_enabled);
 
 	/*
@@ -2397,6 +2701,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops)
 
 	spin_unlock_irq(&scx_tasks_lock);
 	preempt_enable();
+	scx_cgroup_unlock();
 	percpu_up_write(&scx_fork_rwsem);
 
 	if (!scx_ops_tryset_enable_state(SCX_OPS_ENABLED, SCX_OPS_ENABLING)) {
@@ -2410,6 +2715,8 @@ static int scx_ops_enable(struct sched_ext_ops *ops)
 	cpus_read_unlock();
 	mutex_unlock(&scx_ops_enable_mutex);
 
+	scx_cgroup_config_knobs();
+
 	return 0;
 
 err_unlock:
@@ -2417,6 +2724,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops)
 	return ret;
 
 err_disable_unlock:
+	scx_cgroup_unlock();
 	percpu_up_write(&scx_fork_rwsem);
 err_disable:
 	cpus_read_unlock();
@@ -2578,6 +2886,9 @@ static int bpf_scx_check_member(const struct btf_type *t,
 
 	switch (moff) {
 	case offsetof(struct sched_ext_ops, prep_enable):
+	case offsetof(struct sched_ext_ops, cgroup_init):
+	case offsetof(struct sched_ext_ops, cgroup_exit):
+	case offsetof(struct sched_ext_ops, cgroup_prep_move):
 	case offsetof(struct sched_ext_ops, init):
 	case offsetof(struct sched_ext_ops, exit):
 		/*
@@ -2704,6 +3015,7 @@ void __init init_sched_ext_class(void)
 
 	register_sysrq_key('S', &sysrq_sched_ext_reset_op);
 	INIT_DELAYED_WORK(&check_timeout_work, scx_check_timeout_workfn);
+	scx_cgroup_config_knobs();
 }
 
 
@@ -2745,7 +3057,7 @@ static const struct btf_kfunc_id_set scx_kfunc_set_init = {
  * @node: NUMA node to allocate from
  *
  * Create a dsq identified by @dsq_id. Can be called from sleepable operations
- * including ops.init() and .prep_enable().
+ * including ops.init(), .prep_enable() and .cgroup_prep_move().
  */
 s32 scx_bpf_create_dsq(u64 dsq_id, s32 node)
 {
diff --git a/kernel/sched/ext.h b/kernel/sched/ext.h
index e9ec267f13d5..470b2224cdfa 100644
--- a/kernel/sched/ext.h
+++ b/kernel/sched/ext.h
@@ -59,6 +59,11 @@ enum scx_deq_flags {
 	SCX_DEQ_SLEEP		= DEQUEUE_SLEEP,
 };
 
+enum scx_tg_flags {
+	SCX_TG_ONLINE		= 1U << 0,
+	SCX_TG_INITED		= 1U << 1,
+};
+
 enum scx_kick_flags {
 	SCX_KICK_PREEMPT	= 1LLU << 0,	/* force scheduling on the CPU */
 };
@@ -185,3 +190,21 @@ static inline void scx_update_idle(struct rq *rq, bool idle)
 #else
 static inline void scx_update_idle(struct rq *rq, bool idle) {}
 #endif
+
+#ifdef CONFIG_EXT_GROUP_SCHED
+int scx_tg_online(struct task_group *tg);
+void scx_tg_offline(struct task_group *tg);
+int scx_cgroup_can_attach(struct cgroup_taskset *tset);
+void scx_cgroup_move_task(struct task_struct *p);
+void scx_cgroup_finish_attach(void);
+void scx_cgroup_cancel_attach(struct cgroup_taskset *tset);
+void scx_group_set_weight(struct task_group *tg, unsigned long cgrp_weight);
+#else	/* CONFIG_EXT_GROUP_SCHED */
+static inline int scx_tg_online(struct task_group *tg) { return 0; }
+static inline void scx_tg_offline(struct task_group *tg) {}
+static inline int scx_cgroup_can_attach(struct cgroup_taskset *tset) { return 0; }
+static inline void scx_cgroup_move_task(struct task_struct *p) {}
+static inline void scx_cgroup_finish_attach(void) {}
+static inline void scx_cgroup_cancel_attach(struct cgroup_taskset *tset) {}
+static inline void scx_group_set_weight(struct task_group *tg, unsigned long cgrp_weight) {}
+#endif	/* CONFIG_EXT_GROUP_SCHED */
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index a95aae3bc69a..a2ffa94ede02 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -406,6 +406,11 @@ struct task_group {
 	struct rt_bandwidth	rt_bandwidth;
 #endif
 
+#ifdef CONFIG_EXT_GROUP_SCHED
+	u32			scx_flags;	/* SCX_TG_* */
+	u32			scx_weight;
+#endif
+
 	struct rcu_head		rcu;
 	struct list_head	list;
 
@@ -535,6 +540,11 @@ extern void set_task_rq_fair(struct sched_entity *se,
 static inline void set_task_rq_fair(struct sched_entity *se,
 			     struct cfs_rq *prev, struct cfs_rq *next) { }
 #endif /* CONFIG_SMP */
+#else /* CONFIG_FAIR_GROUP_SCHED */
+static inline int sched_group_set_shares(struct task_group *tg, unsigned long shares)
+{
+	return 0;
+}
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
 #else /* CONFIG_CGROUP_SCHED */
@@ -3260,7 +3270,7 @@ static inline void update_current_exec_runtime(struct task_struct *curr,
 
 #ifdef CONFIG_CGROUP_SCHED
 enum cpu_cftype_id {
-#ifdef CONFIG_FAIR_GROUP_SCHED
+#if defined(CONFIG_FAIR_GROUP_SCHED) || defined(CONFIG_EXT_GROUP_SCHED)
 	CPU_CFTYPE_WEIGHT,
 	CPU_CFTYPE_WEIGHT_NICE,
 	CPU_CFTYPE_IDLE,
diff --git a/tools/sched_ext/.gitignore b/tools/sched_ext/.gitignore
index 389f0e5b0970..ebc34dcf925b 100644
--- a/tools/sched_ext/.gitignore
+++ b/tools/sched_ext/.gitignore
@@ -1,6 +1,7 @@
 scx_example_dummy
 scx_example_qmap
 scx_example_central
+scx_example_pair
 *.skel.h
 *.subskel.h
 /tools/
diff --git a/tools/sched_ext/Makefile b/tools/sched_ext/Makefile
index d406b7586e08..45ab39139afc 100644
--- a/tools/sched_ext/Makefile
+++ b/tools/sched_ext/Makefile
@@ -114,7 +114,7 @@ BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH)					\
 	     -Wno-compare-distinct-pointer-types				\
 	     -O2 -mcpu=v3
 
-all: scx_example_dummy scx_example_qmap scx_example_central
+all: scx_example_dummy scx_example_qmap scx_example_central scx_example_pair
 
 # sort removes libbpf duplicates when not cross-building
 MAKE_DIRS := $(sort $(BUILD_DIR)/libbpf $(HOST_BUILD_DIR)/libbpf		\
@@ -177,10 +177,15 @@ scx_example_central: scx_example_central.c scx_example_central.skel.h user_exit_
 	$(CC) $(CFLAGS) -c $< -o $@.o
 	$(CC) -o $@ $@.o $(HOST_BPFOBJ) $(LDFLAGS)
 
+scx_example_pair: scx_example_pair.c scx_example_pair.skel.h user_exit_info.h
+	$(CC) $(CFLAGS) -c $< -o $@.o
+	$(CC) -o $@ $@.o $(HOST_BPFOBJ) $(LDFLAGS)
+
 clean:
 	rm -rf $(SCRATCH_DIR) $(HOST_SCRATCH_DIR)
 	rm -f *.o *.bpf.o *.skel.h *.subskel.h
-	rm -f scx_example_dummy scx_example_qmap scx_example_central
+	rm -f scx_example_dummy scx_example_qmap scx_example_central		\
+	      scx_example_pair
 
 .PHONY: all clean
 
diff --git a/tools/sched_ext/scx_example_pair.bpf.c b/tools/sched_ext/scx_example_pair.bpf.c
new file mode 100644
index 000000000000..7694d2169383
--- /dev/null
+++ b/tools/sched_ext/scx_example_pair.bpf.c
@@ -0,0 +1,554 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * A demo sched_ext core-scheduler which always makes every sibling CPU pair
+ * execute from the same CPU cgroup.
+ *
+ * Each CPU in the system is paired with exactly one other CPU, according to a
+ * "stride" value that can be specified when the BPF scheduler program is first
+ * loaded. Throughout the runtime of the scheduler, these CPU pairs guarantee
+ * that they will only ever schedule tasks that belong to the same CPU cgroup.
+ *
+ * Scheduler Initialization
+ * ------------------------
+ *
+ * The scheduler BPF program is first initialized from user space, before it is
+ * enabled. During this initialization process, each CPU on the system is
+ * assigned several values that are constant throughout its runtime:
+ *
+ * 1. *Pair CPU*: The CPU that it synchronizes with when making scheduling
+ *		  decisions. Paired CPUs always schedule tasks from the same
+ *		  CPU cgroup, and synchronize with each other to guarantee
+ *		  that this constraint is not violated.
+ * 2. *Pair ID*:  Each CPU pair is assigned a Pair ID, which is used to access
+ *		  a struct pair_ctx object that is shared between the pair.
+ * 3. *In-pair-index*: An index, 0 or 1, that is assigned to each core in the
+ *		       pair. Each struct pair_ctx has an active_mask field,
+ *		       which is a bitmap used to indicate whether each core
+ *		       in the pair currently has an actively running task.
+ *		       This index specifies which entry in the bitmap corresponds
+ *		       to each CPU in the pair.
+ *
+ * During this initialization, the CPUs are paired according to a "stride" that
+ * may be specified when invoking the user space program that initializes and
+ * loads the scheduler. By default, the stride is 1/2 the total number of CPUs.
+ *
+ * Tasks and cgroups
+ * -----------------
+ *
+ * Every cgroup in the system is registered with the scheduler using the
+ * pair_cgroup_init() callback, and every task in the system is associated with
+ * exactly one cgroup. At a high level, the idea with the pair scheduler is to
+ * always schedule tasks from the same cgroup within a given CPU pair. When a
+ * task is enqueued (i.e. passed to the pair_enqueue() callback function), its
+ * cgroup ID is read from its task struct, and then a corresponding queue map
+ * is used to FIFO-enqueue the task for that cgroup.
+ *
+ * If you look through the implementation of the scheduler, you'll notice that
+ * there is quite a bit of complexity involved with looking up the per-cgroup
+ * FIFO queue that we enqueue tasks in. For example, there is a cgrp_q_idx_hash
+ * BPF hash map that is used to map a cgroup ID to a globally unique ID that's
+ * allocated in the BPF program. This is done because we use separate maps to
+ * store the FIFO queue of tasks, and the length of that map, per cgroup. This
+ * complexity is only present because of current deficiencies in BPF that will
+ * soon be addressed. The main point to keep in mind is that newly enqueued
+ * tasks are added to their cgroup's FIFO queue.
+ *
+ * Dispatching tasks
+ * -----------------
+ *
+ * This section will describe how enqueued tasks are dispatched and scheduled.
+ * Tasks are dispatched in pair_dispatch(), and at a high level the workflow is
+ * as follows:
+ *
+ * 1. Fetch the struct pair_ctx for the current CPU. As mentioned above, this is
+ *    the structure that's used to synchronize amongst the two pair CPUs in their
+ *    scheduling decisions. After any of the following events have occurred:
+ *
+ * - The cgroup's slice run has expired, or
+ * - The cgroup becomes empty, or
+ * - Either CPU in the pair is preempted by a higher priority scheduling class
+ *
+ * The cgroup transitions to the draining state and stops executing new tasks
+ * from the cgroup.
+ *
+ * 2. If the pair is still executing a task, mark the pair_ctx as draining, and
+ *    wait for the pair CPU to be preempted.
+ *
+ * 3. Otherwise, if the pair CPU is not running a task, we can move onto
+ *    scheduling new tasks. Pop the next cgroup id from the top_q queue.
+ *
+ * 4. Pop a task from that cgroup's FIFO task queue, and begin executing it.
+ *
+ * Note again that this scheduling behavior is simple, but the implementation
+ * is complex mostly because this it hits several BPF shortcomings and has to
+ * work around in often awkward ways. Most of the shortcomings are expected to
+ * be resolved in the near future which should allow greatly simplifying this
+ * scheduler.
+ *
+ * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
+ * Copyright (c) 2022 Tejun Heo <tj@kernel.org>
+ * Copyright (c) 2022 David Vernet <dvernet@meta.com>
+ */
+#include "scx_common.bpf.h"
+#include "scx_example_pair.h"
+
+char _license[] SEC("license") = "GPL";
+
+const volatile bool switch_all;
+
+const volatile u32 nr_cpu_ids;
+
+/* a pair of CPUs stay on a cgroup for this duration */
+const volatile u32 pair_batch_dur_ns = SCX_SLICE_DFL;
+
+/* cpu ID -> pair cpu ID */
+const volatile s32 pair_cpu[MAX_CPUS] = { [0 ... MAX_CPUS - 1] = -1 };
+
+/* cpu ID -> pair_id */
+const volatile u32 pair_id[MAX_CPUS];
+
+/* CPU ID -> CPU # in the pair (0 or 1) */
+const volatile u32 in_pair_idx[MAX_CPUS];
+
+struct pair_ctx {
+	struct bpf_spin_lock	lock;
+
+	/* the cgroup the pair is currently executing */
+	u64			cgid;
+
+	/* the pair started executing the current cgroup at */
+	u64			started_at;
+
+	/* whether the current cgroup is draining */
+	bool			draining;
+
+	/* the CPUs that are currently active on the cgroup */
+	u32			active_mask;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, MAX_CPUS / 2);
+	__type(key, u32);
+	__type(value, struct pair_ctx);
+} pair_ctx SEC(".maps");
+
+/* queue of cgrp_q's possibly with tasks on them */
+struct {
+	__uint(type, BPF_MAP_TYPE_QUEUE);
+	/*
+	 * Because it's difficult to build strong synchronization encompassing
+	 * multiple non-trivial operations in BPF, this queue is managed in an
+	 * opportunistic way so that we guarantee that a cgroup w/ active tasks
+	 * is always on it but possibly multiple times. Once we have more robust
+	 * synchronization constructs and e.g. linked list, we should be able to
+	 * do this in a prettier way but for now just size it big enough.
+	 */
+	__uint(max_entries, 4 * MAX_CGRPS);
+	__type(value, u64);
+} top_q SEC(".maps");
+
+/* per-cgroup q which FIFOs the tasks from the cgroup */
+struct cgrp_q {
+	__uint(type, BPF_MAP_TYPE_QUEUE);
+	__uint(max_entries, MAX_QUEUED);
+	__type(value, u32);
+};
+
+/*
+ * Ideally, we want to allocate cgrp_q and cgrq_q_len in the cgroup local
+ * storage; however, a cgroup local storage can only be accessed from the BPF
+ * progs attached to the cgroup. For now, work around by allocating array of
+ * cgrp_q's and then allocating per-cgroup indices.
+ *
+ * Another caveat: It's difficult to populate a large array of maps statically
+ * or from BPF. Initialize it from userland.
+ */
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+	__uint(max_entries, MAX_CGRPS);
+	__type(key, s32);
+	__array(values, struct cgrp_q);
+} cgrp_q_arr SEC(".maps");
+
+static u64 cgrp_q_len[MAX_CGRPS];
+
+/*
+ * This and cgrp_q_idx_hash combine into a poor man's IDR. This likely would be
+ * useful to have as a map type.
+ */
+static u32 cgrp_q_idx_cursor;
+static u64 cgrp_q_idx_busy[MAX_CGRPS];
+
+/*
+ * All added up, the following is what we do:
+ *
+ * 1. When a cgroup is enabled, RR cgroup_q_idx_busy array doing cmpxchg looking
+ *    for a free ID. If not found, fail cgroup creation with -EBUSY.
+ *
+ * 2. Hash the cgroup ID to the allocated cgrp_q_idx in the following
+ *    cgrp_q_idx_hash.
+ *
+ * 3. Whenever a cgrp_q needs to be accessed, first look up the cgrp_q_idx from
+ *    cgrp_q_idx_hash and then access the corresponding entry in cgrp_q_arr.
+ *
+ * This is sadly complicated for something pretty simple. Hopefully, we should
+ * be able to simplify in the future.
+ */
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, MAX_CGRPS);
+	__uint(key_size, sizeof(u64));		/* cgrp ID */
+	__uint(value_size, sizeof(s32));	/* cgrp_q idx */
+} cgrp_q_idx_hash SEC(".maps");
+
+/* statistics */
+u64 nr_total, nr_dispatched, nr_missing, nr_kicks, nr_preemptions;
+u64 nr_exps, nr_exp_waits, nr_exp_empty;
+u64 nr_cgrp_next, nr_cgrp_coll, nr_cgrp_empty;
+
+struct user_exit_info uei;
+
+static bool time_before(u64 a, u64 b)
+{
+	return (s64)(a - b) < 0;
+}
+
+void BPF_STRUCT_OPS(pair_enqueue, struct task_struct *p, u64 enq_flags)
+{
+	s32 pid = p->pid;
+	u64 cgid = p->sched_task_group->css.cgroup->kn->id;
+	u32 *q_idx;
+	struct cgrp_q *cgq;
+	u64 *cgq_len;
+
+	__sync_fetch_and_add(&nr_total, 1);
+
+	/* find the cgroup's q and push @p into it */
+	q_idx = bpf_map_lookup_elem(&cgrp_q_idx_hash, &cgid);
+	if (!q_idx) {
+		scx_bpf_error("failed to lookup q_idx for cgroup[%llu]", cgid);
+		return;
+	}
+
+	cgq = bpf_map_lookup_elem(&cgrp_q_arr, q_idx);
+	if (!cgq) {
+		scx_bpf_error("failed to lookup q_arr for cgroup[%llu] q_idx[%u]",
+			      cgid, *q_idx);
+		return;
+	}
+
+	if (bpf_map_push_elem(cgq, &pid, 0)) {
+		scx_bpf_error("cgroup[%llu] queue overflow", cgid);
+		return;
+	}
+
+	/* bump q len, if going 0 -> 1, queue cgroup into the top_q */
+	cgq_len = MEMBER_VPTR(cgrp_q_len, [*q_idx]);
+	if (!cgq_len) {
+		scx_bpf_error("MEMBER_VTPR malfunction");
+		return;
+	}
+
+	if (!__sync_fetch_and_add(cgq_len, 1) &&
+	    bpf_map_push_elem(&top_q, &cgid, 0)) {
+		scx_bpf_error("top_q overflow");
+		return;
+	}
+}
+
+/* find the next cgroup to execute and return it in *data */
+static int next_cgid_loopfn(u32 idx, void *data)
+{
+	u64 cgid;
+	u32 *q_idx;
+	u64 *cgq_len;
+
+	if (bpf_map_pop_elem(&top_q, &cgid))
+		return 1;
+
+	q_idx = bpf_map_lookup_elem(&cgrp_q_idx_hash, &cgid);
+	if (!q_idx)
+		return 0;
+
+	/* this is the only place where empty cgroups are taken off the top_q */
+	cgq_len = MEMBER_VPTR(cgrp_q_len, [*q_idx]);
+	if (!cgq_len || !*cgq_len)
+		return 0;
+
+	/* if it has any tasks, requeue as we may race and not execute it */
+	bpf_map_push_elem(&top_q, &cgid, 0);
+	*(u64 *)data = cgid;
+	return 1;
+}
+
+struct claim_task_loopctx {
+	u32		q_idx;
+	bool		claimed;
+};
+
+/* claim one task from the specified cgq */
+static int claim_task_loopfn(u32 idx, void *data)
+{
+	struct claim_task_loopctx *claimc = data;
+	u64 *cgq_len;
+	u64 len;
+
+	cgq_len = MEMBER_VPTR(cgrp_q_len, [claimc->q_idx]);
+	if (!cgq_len)
+		return 1;
+
+	len = *cgq_len;
+	if (!len)
+		return 1;
+
+	if (__sync_val_compare_and_swap(cgq_len, len, len - 1) != len)
+		return 0;
+
+	claimc->claimed = true;
+	return 1;
+}
+
+static int lookup_pairc_and_mask(s32 cpu, struct pair_ctx **pairc, u32 *mask)
+{
+	u32 *vptr, in_pair_mask;
+	int err;
+
+	vptr = (u32 *)MEMBER_VPTR(pair_id, [cpu]);
+	if (!vptr)
+		return -EINVAL;
+
+	*pairc = bpf_map_lookup_elem(&pair_ctx, vptr);
+	if (!(*pairc))
+		return -EINVAL;
+
+	vptr = (u32 *)MEMBER_VPTR(in_pair_idx, [cpu]);
+	if (!vptr)
+		return -EINVAL;
+
+	*mask = 1U << *vptr;
+
+	return 0;
+}
+
+static int dispatch_loopfn(u32 idx, void *data)
+{
+	s32 cpu = *(s32 *)data;
+	struct pair_ctx *pairc;
+	struct bpf_map *cgq_map;
+	struct claim_task_loopctx claimc;
+	struct task_struct *p;
+	u64 now = bpf_ktime_get_ns();
+	bool kick_pair = false;
+	bool expired;
+	u32 *vptr, in_pair_mask;
+	s32 pid;
+	u64 cgid;
+	int ret;
+
+	ret = lookup_pairc_and_mask(cpu, &pairc, &in_pair_mask);
+	if (ret) {
+		scx_bpf_error("failed to lookup pairc and in_pair_mask for cpu[%d]",
+			      cpu);
+		return 1;
+	}
+
+	bpf_spin_lock(&pairc->lock);
+	pairc->active_mask &= ~in_pair_mask;
+
+	expired = time_before(pairc->started_at + pair_batch_dur_ns, now);
+	if (expired || pairc->draining) {
+		u64 new_cgid = 0;
+
+		__sync_fetch_and_add(&nr_exps, 1);
+
+		/*
+		 * We're done with the current cgid. An obvious optimization
+		 * would be not draining if the next cgroup is the current one.
+		 * For now, be dumb and always expire.
+		 */
+		pairc->draining = true;
+
+		if (pairc->active_mask) {
+			/*
+			 * The other CPU is still active We want to wait until
+			 * this cgroup expires.
+			 *
+			 * If the pair controls its CPU, and the time already
+			 * expired, kick.  When the other CPU arrives at
+			 * dispatch and clears its active mask, it'll push the
+			 * pair to the next cgroup and kick this CPU.
+			 */
+			__sync_fetch_and_add(&nr_exp_waits, 1);
+			bpf_spin_unlock(&pairc->lock);
+			if (expired)
+				kick_pair = true;
+			goto out_maybe_kick;
+		}
+
+		bpf_spin_unlock(&pairc->lock);
+
+		/*
+		 * Pick the next cgroup. It'd be easier / cleaner to not drop
+		 * pairc->lock and use stronger synchronization here especially
+		 * given that we'll be switching cgroups significantly less
+		 * frequently than tasks. Unfortunately, bpf_spin_lock can't
+		 * really protect anything non-trivial. Let's do opportunistic
+		 * operations instead.
+		 */
+		bpf_loop(1 << 23, next_cgid_loopfn, &new_cgid, 0);
+		/* no active cgroup, go idle */
+		if (!new_cgid) {
+			__sync_fetch_and_add(&nr_exp_empty, 1);
+			return 1;
+		}
+
+		bpf_spin_lock(&pairc->lock);
+
+		/*
+		 * The other CPU may already have started on a new cgroup while
+		 * we dropped the lock. Make sure that we're still draining and
+		 * start on the new cgroup.
+		 */
+		if (pairc->draining && !pairc->active_mask) {
+			__sync_fetch_and_add(&nr_cgrp_next, 1);
+			pairc->cgid = new_cgid;
+			pairc->started_at = now;
+			pairc->draining = false;
+			kick_pair = true;
+		} else {
+			__sync_fetch_and_add(&nr_cgrp_coll, 1);
+		}
+	}
+
+	cgid = pairc->cgid;
+	pairc->active_mask |= in_pair_mask;
+	bpf_spin_unlock(&pairc->lock);
+
+	/* again, it'd be better to do all these with the lock held, oh well */
+	vptr = bpf_map_lookup_elem(&cgrp_q_idx_hash, &cgid);
+	if (!vptr) {
+		scx_bpf_error("failed to lookup q_idx for cgroup[%llu]", cgid);
+		return 1;
+	}
+
+	claimc = (struct claim_task_loopctx){ .q_idx = *vptr };
+	bpf_loop(1 << 23, claim_task_loopfn, &claimc, 0);
+	if (!claimc.claimed) {
+		/* the cgroup must be empty, expire and repeat */
+		__sync_fetch_and_add(&nr_cgrp_empty, 1);
+		bpf_spin_lock(&pairc->lock);
+		pairc->draining = true;
+		pairc->active_mask &= ~in_pair_mask;
+		bpf_spin_unlock(&pairc->lock);
+		return 0;
+	}
+
+	cgq_map = bpf_map_lookup_elem(&cgrp_q_arr, &claimc.q_idx);
+	if (!cgq_map) {
+		scx_bpf_error("failed to lookup cgq_map for cgroup[%llu] q_idx[%d]",
+			      cgid, claimc.q_idx);
+		return 1;
+	}
+
+	if (bpf_map_pop_elem(cgq_map, &pid)) {
+		scx_bpf_error("cgq_map is empty for cgroup[%llu] q_idx[%d]",
+			      cgid, claimc.q_idx);
+		return 1;
+	}
+
+	p = scx_bpf_find_task_by_pid(pid);
+	if (p) {
+		__sync_fetch_and_add(&nr_dispatched, 1);
+		scx_bpf_dispatch(p, SCX_DSQ_GLOBAL, SCX_SLICE_DFL, 0);
+	} else {
+		/* we don't handle dequeues, retry on lost tasks */
+		__sync_fetch_and_add(&nr_missing, 1);
+		return 0;
+	}
+
+out_maybe_kick:
+	if (kick_pair) {
+		s32 *pair = (s32 *)MEMBER_VPTR(pair_cpu, [cpu]);
+		if (pair) {
+			__sync_fetch_and_add(&nr_kicks, 1);
+			scx_bpf_kick_cpu(*pair, SCX_KICK_PREEMPT);
+		}
+	}
+	return 1;
+}
+
+void BPF_STRUCT_OPS(pair_dispatch, s32 cpu, struct task_struct *prev)
+{
+	s32 cpu_on_stack = cpu;
+
+	bpf_loop(1 << 23, dispatch_loopfn, &cpu_on_stack, 0);
+}
+
+static int alloc_cgrp_q_idx_loopfn(u32 idx, void *data)
+{
+	u32 q_idx;
+
+	q_idx = __sync_fetch_and_add(&cgrp_q_idx_cursor, 1) % MAX_CGRPS;
+	if (!__sync_val_compare_and_swap(&cgrp_q_idx_busy[q_idx], 0, 1)) {
+		*(s32 *)data = q_idx;
+		return 1;
+	}
+	return 0;
+}
+
+s32 BPF_STRUCT_OPS(pair_cgroup_init, struct cgroup *cgrp)
+{
+	u64 cgid = cgrp->kn->id;
+	s32 q_idx = -1;
+
+	bpf_loop(MAX_CGRPS, alloc_cgrp_q_idx_loopfn, &q_idx, 0);
+	if (q_idx < 0)
+		return -EBUSY;
+
+	if (bpf_map_update_elem(&cgrp_q_idx_hash, &cgid, &q_idx, BPF_ANY)) {
+		u64 *busy = MEMBER_VPTR(cgrp_q_idx_busy, [q_idx]);
+		if (busy)
+			*busy = 0;
+		return -EBUSY;
+	}
+
+	return 0;
+}
+
+void BPF_STRUCT_OPS(pair_cgroup_exit, struct cgroup *cgrp)
+{
+	u64 cgid = cgrp->kn->id;
+	s32 *q_idx;
+
+	q_idx = bpf_map_lookup_elem(&cgrp_q_idx_hash, &cgid);
+	if (q_idx) {
+		u64 *busy = MEMBER_VPTR(cgrp_q_idx_busy, [*q_idx]);
+		if (busy)
+			*busy = 0;
+		bpf_map_delete_elem(&cgrp_q_idx_hash, &cgid);
+	}
+}
+
+s32 BPF_STRUCT_OPS(pair_init)
+{
+	if (switch_all)
+		scx_bpf_switch_all();
+	return 0;
+}
+
+void BPF_STRUCT_OPS(pair_exit, struct scx_exit_info *ei)
+{
+	uei_record(&uei, ei);
+}
+
+SEC(".struct_ops")
+struct sched_ext_ops pair_ops = {
+	.enqueue		= (void *)pair_enqueue,
+	.dispatch		= (void *)pair_dispatch,
+	.cgroup_init		= (void *)pair_cgroup_init,
+	.cgroup_exit		= (void *)pair_cgroup_exit,
+	.init			= (void *)pair_init,
+	.exit			= (void *)pair_exit,
+	.name			= "pair",
+};
diff --git a/tools/sched_ext/scx_example_pair.c b/tools/sched_ext/scx_example_pair.c
new file mode 100644
index 000000000000..255ea7b1235d
--- /dev/null
+++ b/tools/sched_ext/scx_example_pair.c
@@ -0,0 +1,143 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
+ * Copyright (c) 2022 Tejun Heo <tj@kernel.org>
+ * Copyright (c) 2022 David Vernet <dvernet@meta.com>
+ */
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <unistd.h>
+#include <signal.h>
+#include <assert.h>
+#include <libgen.h>
+#include <bpf/bpf.h>
+#include "user_exit_info.h"
+#include "scx_example_pair.h"
+#include "scx_example_pair.skel.h"
+
+const char help_fmt[] =
+"A demo sched_ext core-scheduler which always makes every sibling CPU pair\n"
+"execute from the same CPU cgroup.\n"
+"\n"
+"See the top-level comment in .bpf.c for more details.\n"
+"\n"
+"Usage: %s [-a] [-S STRIDE]\n"
+"\n"
+"  -a            Switch all tasks\n"
+"  -S STRIDE     Override CPU pair stride (default: nr_cpus_ids / 2)\n"
+"  -h            Display this help and exit\n";
+
+static volatile int exit_req;
+
+static void sigint_handler(int dummy)
+{
+	exit_req = 1;
+}
+
+int main(int argc, char **argv)
+{
+	struct scx_example_pair *skel;
+	struct bpf_link *link;
+	u64 seq = 0;
+	s32 stride, i, opt, outer_fd;
+
+	signal(SIGINT, sigint_handler);
+	signal(SIGTERM, sigint_handler);
+
+	libbpf_set_strict_mode(LIBBPF_STRICT_ALL);
+
+	skel = scx_example_pair__open();
+	assert(skel);
+
+	skel->rodata->nr_cpu_ids = libbpf_num_possible_cpus();
+
+	/* pair up the earlier half to the latter by default, override with -s */
+	stride = skel->rodata->nr_cpu_ids / 2;
+
+	while ((opt = getopt(argc, argv, "ahS:")) != -1) {
+		switch (opt) {
+		case 'a':
+			skel->rodata->switch_all = true;
+			break;
+		case 'S':
+			stride = strtoul(optarg, NULL, 0);
+			break;
+		default:
+			fprintf(stderr, help_fmt, basename(argv[0]));
+			return opt != 'h';
+		}
+	}
+
+	for (i = 0; i < skel->rodata->nr_cpu_ids; i++) {
+		if (skel->rodata->pair_cpu[i] < 0) {
+			skel->rodata->pair_cpu[i] = i + stride;
+			skel->rodata->pair_cpu[i + stride] = i;
+			skel->rodata->pair_id[i] = i;
+			skel->rodata->pair_id[i + stride] = i;
+			skel->rodata->in_pair_idx[i] = 0;
+			skel->rodata->in_pair_idx[i + stride] = 1;
+		}
+	}
+
+	assert(!scx_example_pair__load(skel));
+
+	/*
+	 * Populate the cgrp_q_arr map which is an array containing per-cgroup
+	 * queues. It'd probably be better to do this from BPF but there are too
+	 * many to initialize statically and there's no way to dynamically
+	 * populate from BPF.
+	 */
+	outer_fd = bpf_map__fd(skel->maps.cgrp_q_arr);
+	assert(outer_fd >= 0);
+
+	printf("Initializing");
+        for (i = 0; i < MAX_CGRPS; i++) {
+		s32 inner_fd;
+
+		if (exit_req)
+			break;
+
+		inner_fd = bpf_map_create(BPF_MAP_TYPE_QUEUE, NULL, 0,
+					  sizeof(u32), MAX_QUEUED, NULL);
+		assert(inner_fd >= 0);
+		assert(!bpf_map_update_elem(outer_fd, &i, &inner_fd, BPF_ANY));
+		close(inner_fd);
+
+		if (!(i % 10))
+			printf(".");
+		fflush(stdout);
+        }
+	printf("\n");
+
+	/*
+	 * Fully initialized, attach and run.
+	 */
+	link = bpf_map__attach_struct_ops(skel->maps.pair_ops);
+	assert(link);
+
+	while (!exit_req && !uei_exited(&skel->bss->uei)) {
+		printf("[SEQ %lu]\n", seq++);
+		printf(" total:%10lu dispatch:%10lu   missing:%10lu\n",
+		       skel->bss->nr_total,
+		       skel->bss->nr_dispatched,
+		       skel->bss->nr_missing);
+		printf(" kicks:%10lu preemptions:%7lu\n",
+		       skel->bss->nr_kicks,
+		       skel->bss->nr_preemptions);
+		printf("   exp:%10lu exp_wait:%10lu exp_empty:%10lu\n",
+		       skel->bss->nr_exps,
+		       skel->bss->nr_exp_waits,
+		       skel->bss->nr_exp_empty);
+		printf("cgnext:%10lu   cgcoll:%10lu   cgempty:%10lu\n",
+		       skel->bss->nr_cgrp_next,
+		       skel->bss->nr_cgrp_coll,
+		       skel->bss->nr_cgrp_empty);
+		fflush(stdout);
+		sleep(1);
+	}
+
+	bpf_link__destroy(link);
+	uei_print(&skel->bss->uei);
+	scx_example_pair__destroy(skel);
+	return 0;
+}
diff --git a/tools/sched_ext/scx_example_pair.h b/tools/sched_ext/scx_example_pair.h
new file mode 100644
index 000000000000..f60b824272f7
--- /dev/null
+++ b/tools/sched_ext/scx_example_pair.h
@@ -0,0 +1,10 @@
+#ifndef __SCX_EXAMPLE_PAIR_H
+#define __SCX_EXAMPLE_PAIR_H
+
+enum {
+	MAX_CPUS		= 4096,
+	MAX_QUEUED		= 4096,
+	MAX_CGRPS		= 4096,
+};
+
+#endif /* __SCX_EXAMPLE_PAIR_H */
