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sched/cpuset: Keep track of SCHED_DEADLINE task in cpusets

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commit 6c24849f5515e4966d94fa5279bdff4acf2e9489 upstream.

Qais reported that iterating over all tasks when rebuilding root domains
for finding out which ones are DEADLINE and need their bandwidth
correctly restored on such root domains can be a costly operation (10+
ms delays on suspend-resume).

To fix the problem keep track of the number of DEADLINE tasks belonging
to each cpuset and then use this information (followup patch) to only
perform the above iteration if DEADLINE tasks are actually present in
the cpuset for which a corresponding root domain is being rebuilt.

Reported-by: Qais Yousef (Google) <qyousef@layalina.io>
Link: https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef@layalina.io/
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
[ Fix conflicts in kernel/cgroup/cpuset.c and kernel/sched/deadline.c
  due to pulling new fields and functions. Remove new code and match the
  patch diff. ]
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Juri Lelli
2023-08-20 16:21:41 +01:00
committed by Greg Kroah-Hartman
parent b950133d9a
commit 5ac05ce568
4 changed files with 46 additions and 0 deletions
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13
kernel/sched/deadline.c
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@@ -17,6 +17,7 @@
*/
#include "sched.h"
#include "pelt.h"
#include <linux/cpuset.h>
struct dl_bandwidth def_dl_bandwidth;
@@ -2417,6 +2418,12 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
if (task_on_rq_queued(p) && p->dl.dl_runtime)
task_non_contending(p);
/*
* In case a task is setscheduled out from SCHED_DEADLINE we need to
* keep track of that on its cpuset (for correct bandwidth tracking).
*/
dec_dl_tasks_cs(p);
if (!task_on_rq_queued(p)) {
/*
* Inactive timer is armed. However, p is leaving DEADLINE and
@@ -2457,6 +2464,12 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
put_task_struct(p);
/*
* In case a task is setscheduled to SCHED_DEADLINE we need to keep
* track of that on its cpuset (for correct bandwidth tracking).
*/
inc_dl_tasks_cs(p);
/* If p is not queued we will update its parameters at next wakeup. */
if (!task_on_rq_queued(p)) {
add_rq_bw(&p->dl, &rq->dl);