Commit 30dd3b13 authored by Henry Huang's avatar Henry Huang Committed by Tejun Heo
Browse files

sched_ext: keep running prev when prev->scx.slice != 0 



When %SCX_OPS_ENQ_LAST is set and prev->scx.slice != 0,
@prev will be dispacthed into the local DSQ in put_prev_task_scx().
However, pick_task_scx() is executed before put_prev_task_scx(),
so it will not pick @prev.
Set %SCX_RQ_BAL_KEEP in balance_one() to ensure that pick_task_scx()
can pick @prev.

Signed-off-by: default avatarHenry Huang <henry.hj@antgroup.com>
Acked-by: default avatarAndrea Righi <arighi@nvidia.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent ce2b93fc

kernel/sched/ext.c

+7 −4
Original line number Diff line number Diff line
@@ -2747,6 +2747,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev) 
{

	struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx);

	bool prev_on_scx = prev->sched_class == &ext_sched_class;

	bool prev_on_rq = prev->scx.flags & SCX_TASK_QUEUED;

	int nr_loops = SCX_DSP_MAX_LOOPS;



	lockdep_assert_rq_held(rq);
@@ -2779,8 +2780,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev) 
		 * See scx_ops_disable_workfn() for the explanation on the

		 * bypassing test.

		 */

		if ((prev->scx.flags & SCX_TASK_QUEUED) &&

		    prev->scx.slice && !scx_rq_bypassing(rq)) {

		if (prev_on_rq && prev->scx.slice && !scx_rq_bypassing(rq)) {

			rq->scx.flags |= SCX_RQ_BAL_KEEP;

			goto has_tasks;

		}
@@ -2813,6 +2813,10 @@ static int balance_one(struct rq *rq, struct task_struct *prev) 


		flush_dispatch_buf(rq);



		if (prev_on_rq && prev->scx.slice) {

			rq->scx.flags |= SCX_RQ_BAL_KEEP;

			goto has_tasks;

		}

		if (rq->scx.local_dsq.nr)

			goto has_tasks;

		if (consume_global_dsq(rq))
@@ -2838,8 +2842,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev) 
	 * Didn't find another task to run. Keep running @prev unless

	 * %SCX_OPS_ENQ_LAST is in effect.

	 */

	if ((prev->scx.flags & SCX_TASK_QUEUED) &&

	    (!static_branch_unlikely(&scx_ops_enq_last) ||

	if (prev_on_rq && (!static_branch_unlikely(&scx_ops_enq_last) ||

	     scx_rq_bypassing(rq))) {

		rq->scx.flags |= SCX_RQ_BAL_KEEP;

		goto has_tasks;