Commit 5dd74441 authored by Guopeng Zhang's avatar Guopeng Zhang Committed by Tejun Heo
Browse files

cgroup/cpuset: Reserve DL bandwidth only for root-domain moves 



cpuset_can_attach() currently adds the bandwidth of all migrating
SCHED_DEADLINE tasks to sum_migrate_dl_bw. If the source and destination
cpuset effective CPU masks do not overlap, the whole sum is then
reserved in the destination root domain.

set_cpus_allowed_dl(), however, subtracts bandwidth from the source
root domain only when the affinity change really moves the task between
root domains. A DL task can move between cpusets that are still in the
same root domain, so including that task in sum_migrate_dl_bw can reserve
destination bandwidth without a matching source-side subtraction.

Share the root-domain move test with set_cpus_allowed_dl(). Keep
nr_migrate_dl_tasks counting all migrating deadline tasks for cpuset DL
task accounting, but add to sum_migrate_dl_bw only for tasks that need a
root-domain bandwidth move. Keep using the destination cpuset effective
CPU mask and leave the broader can_attach()/attach() transaction model
unchanged.

Fixes: 2ef269ef ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Cc: stable@vger.kernel.org # v6.10+
Signed-off-by: default avatarGuopeng Zhang <zhangguopeng@kylinos.cn>
Reviewed-by: default avatarWaiman Long <longman@redhat.com>
Acked-by: default avatarJuri Lelli <juri.lelli@redhat.com>
Tested-by: default avatarJuri Lelli <juri.lelli@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 4a39eda5

include/linux/sched/deadline.h

+9 −0
Original line number Diff line number Diff line
@@ -33,6 +33,15 @@ struct root_domain; 
extern void dl_add_task_root_domain(struct task_struct *p);

extern void dl_clear_root_domain(struct root_domain *rd);

extern void dl_clear_root_domain_cpu(int cpu);

/*

 * Return whether moving DL task @p to @new_mask requires moving DL

 * bandwidth accounting between root domains. This helper is specific to

 * DL bandwidth move accounting semantics and is shared by

 * cpuset_can_attach() and set_cpus_allowed_dl() so both paths use the

 * same source root-domain test.

 */

extern bool dl_task_needs_bw_move(struct task_struct *p,

				  const struct cpumask *new_mask);



extern u64 dl_cookie;

extern bool dl_bw_visited(int cpu, u64 cookie);

kernel/cgroup/cpuset-internal.h

+1 −0
Original line number Diff line number Diff line
@@ -167,6 +167,7 @@ struct cpuset { 
	 */

	int nr_deadline_tasks;

	int nr_migrate_dl_tasks;

	/* DL bandwidth that needs destination reservation for this attach. */

	u64 sum_migrate_dl_bw;

	/*

	 * CPU used for temporary DL bandwidth allocation during attach;

kernel/cgroup/cpuset.c

+18 −15
Original line number Diff line number Diff line
@@ -2993,7 +2993,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) 
	struct cpuset *cs, *oldcs;

	struct task_struct *task;

	bool setsched_check;

	int ret;

	int cpu, ret;



	/* used later by cpuset_attach() */

	cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
@@ -3038,17 +3038,21 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) 
		}



		if (dl_task(task)) {

			/*

			 * Count all migrating DL tasks for cpuset task accounting.

			 * Only tasks that need a root-domain bandwidth move

			 * contribute to sum_migrate_dl_bw.

			 */

			cs->nr_migrate_dl_tasks++;

			if (dl_task_needs_bw_move(task, cs->effective_cpus))

				cs->sum_migrate_dl_bw += task->dl.dl_bw;

		}

	}



	if (!cs->nr_migrate_dl_tasks)

	if (!cs->sum_migrate_dl_bw)

		goto out_success;



	if (!cpumask_intersects(oldcs->effective_cpus, cs->effective_cpus)) {

		int cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus);



	cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus);

	if (unlikely(cpu >= nr_cpu_ids)) {

		ret = -EINVAL;

		goto out_unlock;
@@ -3059,7 +3063,6 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) 
		goto out_unlock;



	cs->dl_bw_cpu = cpu;

	}



out_success:

	/*

kernel/sched/deadline.c

+10 −3
Original line number Diff line number Diff line
@@ -3107,20 +3107,18 @@ static void task_woken_dl(struct rq *rq, struct task_struct *p) 
static void set_cpus_allowed_dl(struct task_struct *p,

				struct affinity_context *ctx)

{

	struct root_domain *src_rd;

	struct rq *rq;



	WARN_ON_ONCE(!dl_task(p));



	rq = task_rq(p);

	src_rd = rq->rd;

	/*

	 * Migrating a SCHED_DEADLINE task between exclusive

	 * cpusets (different root_domains) entails a bandwidth

	 * update. We already made space for us in the destination

	 * domain (see cpuset_can_attach()).

	 */

	if (!cpumask_intersects(src_rd->span, ctx->new_mask)) {

	if (dl_task_needs_bw_move(p, ctx->new_mask)) {

		struct dl_bw *src_dl_b;



		src_dl_b = dl_bw_of(cpu_of(rq));
@@ -3137,6 +3135,15 @@ static void set_cpus_allowed_dl(struct task_struct *p, 
	set_cpus_allowed_common(p, ctx);

}



bool dl_task_needs_bw_move(struct task_struct *p,

			   const struct cpumask *new_mask)

{

	if (!dl_task(p))

		return false;



	return !cpumask_intersects(task_rq(p)->rd->span, new_mask);

}



/* Assumes rq->lock is held */

static void rq_online_dl(struct rq *rq)

{