Messages in this thread | | | Date | Fri, 22 May 2020 11:44:06 +0800 | From | Aaron Lu <> | Subject | Re: [RFC PATCH 07/13] sched: Add core wide task selection and scheduling. |
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On Thu, May 21, 2020 at 10:35:56PM -0400, Joel Fernandes wrote: > Discussed a lot with Vineeth. Below is an improved version of the pick_task() > similification. > > It also handles the following "bug" in the existing code as well that Vineeth > brought up in OSPM: Suppose 2 siblings of a core: rq 1 and rq 2. > > In priority order (high to low), say we have the tasks: > A - untagged (rq 1) > B - tagged (rq 2) > C - untagged (rq 2) > > Say, B and C are in the same scheduling class. > > When the pick_next_task() loop runs, it looks at rq 1 and max is A, A is > tenantively selected for rq 1. Then it looks at rq 2 and the class_pick is B. > But that's not compatible with A. So rq 2 gets forced idle. > > In reality, rq 2 could have run C instead of idle. The fix is to add C to the > tag tree as Peter suggested in OSPM.
I like the idea of adding untagged task to the core tree.
> Updated diff below: > > ---8<----------------------- > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 005d7f7323e2d..625377f393ed3 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -182,9 +182,6 @@ static void sched_core_enqueue(struct rq *rq, struct task_struct *p) > > rq->core->core_task_seq++; > > - if (!p->core_cookie) > - return; > - > node = &rq->core_tree.rb_node; > parent = *node; > > @@ -215,7 +212,7 @@ static void sched_core_dequeue(struct rq *rq, struct task_struct *p) > > void sched_core_add(struct rq *rq, struct task_struct *p) > { > - if (p->core_cookie && task_on_rq_queued(p)) > + if (task_on_rq_queued(p)) > sched_core_enqueue(rq, p); > }
It appears there are other call sites of sched_core_enqueue() where core_cookie is checked: cpu_cgroup_fork() and __sched_write_tag().
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