From: Aaron Lu <ziqianlu@bytedance.com> mainline inclusion from mainline-v6.18-rc1 commit 253b3f587241967a97a971e23b1e2a7d74244fad category: feature bugzilla: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- With the introduction of task based throttle model, task in a throttled hierarchy is allowed to continue to run till it gets throttled on its ret2user path. For this reason, remove those throttled_hierarchy() checks in the following functions so that those tasks can get their turn as normal tasks: dequeue_entities(), check_preempt_wakeup_fair() and yield_to_task_fair(). The benefit of doing it this way is: if those tasks gets the chance to run earlier and if they hold any kernel resources, they can release those resources earlier. The downside is, if they don't hold any kernel resouces, all they can do is to throttle themselves on their way back to user space so the favor to let them run seems not that useful and for check_preempt_wakeup_fair(), that favor may be bad for curr. K Prateek Nayak pointed out prio_changed_fair() can send a throttled task to check_preempt_wakeup_fair(), further tests showed the affinity change path from move_queued_task() can also send a throttled task to check_preempt_wakeup_fair(), that's why the check of task_is_throttled() in that function. Signed-off-by: Aaron Lu <ziqianlu@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Conflicts: kernel/sched/fair.c [Context differences.] Signed-off-by: Wang Tao <wangtao554@huawei.com> --- kernel/sched/fair.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2e4b5d666507..a7d07ec86cb3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7780,7 +7780,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) * Bias pick_next to pick a task from this cfs_rq, as * p is sleeping when it is within its sched_slice. */ - if (task_sleep && se && !throttled_hierarchy(cfs_rq)) + if (task_sleep && se) set_next_buddy(se); break; } @@ -9635,7 +9635,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ * lead to a throttle). This both saves work and prevents false * next-buddy nomination below. */ - if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) + if (task_is_throttled(p)) return; if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK)) { @@ -10594,8 +10594,8 @@ static bool yield_to_task_fair(struct rq *rq, struct task_struct *p) { struct sched_entity *se = &p->se; - /* throttled hierarchies are not runnable */ - if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) + /* !se->on_rq also covers throttled task */ + if (!se->on_rq) return false; /* Tell the scheduler that we'd really like pse to run next. */ -- 2.18.0