Messages in this thread Patch in this message | | | From | Xuewen Yan <> | Subject | [RFC PATCH] sched/fair: update the vruntime to be max vruntime when yield | Date | Wed, 22 Feb 2023 16:03:14 +0800 |
| |
When task call the sched_yield, cfs would set the cfs's skip buddy. If there is no other task call the sched_yield syscall, the task would always be skiped when there are tasks in rq. As a result, the task's vruntime would not be updated for long time, and the cfs's min_vruntime is almost not updated. When this scenario happens, when the yield task had wait for a long time, and other tasks run a long time, once there is other task call the sched_yield, the cfs's skip_buddy is covered, at this time, the first task can run normally, but the task's vruntime is small, as a result, the task would always run, because other task's vruntime is big. This would lead to other tasks can not run for a long time. In order to mitigate this, update the yield_task's vruntime to be cfs's max vruntime. This way, the cfs's min vruntime can be updated as the process running.
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com> --- kernel/sched/fair.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ff4dbbae3b10..a9ff1921fc07 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -670,7 +670,6 @@ static struct sched_entity *__pick_next_entity(struct sched_entity *se) return __node_2_se(next); } -#ifdef CONFIG_SCHED_DEBUG struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) { struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root); @@ -681,6 +680,7 @@ struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) return __node_2_se(last); } +#ifdef CONFIG_SCHED_DEBUG /************************************************************** * Scheduling class statistics methods: */ @@ -7751,8 +7751,18 @@ static void set_next_buddy(struct sched_entity *se) static void set_skip_buddy(struct sched_entity *se) { - for_each_sched_entity(se) - cfs_rq_of(se)->skip = se; + for_each_sched_entity(se) { + struct sched_entity *last; + struct cfs_rq *cfs_rq = cfs_rq_of(se); + + last = __pick_last_entity(cfs_rq); + if (last) { + se->vruntime = last->vruntime; + update_min_vruntime(cfs_rq); + } + + cfs_rq->skip = se; + } } /* -- 2.25.1
| |