Commit f7f61421 authored by Changwoo Min's avatar Changwoo Min Committed by Tejun Heo
Browse files

sched_ext: Add an event, SCX_EV_SELECT_CPU_FALLBACK 



Add a core event, SCX_EV_SELECT_CPU_FALLBACK, which represents how many times
ops.select_cpu() returns a CPU that the task can't use.

__scx_add_event() is used since the caller holds an rq lock,
so the preemption has already been disabled.

Signed-off-by: default avatarChangwoo Min <changwoo@igalia.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 17103b85

include/linux/sched/ext.h

+1 −0
Original line number Diff line number Diff line
@@ -146,6 +146,7 @@ struct sched_ext_entity { 
	u32			weight;

	s32			sticky_cpu;

	s32			holding_cpu;

	s32			selected_cpu;

	u32			kf_mask;	/* see scx_kf_mask above */

	struct task_struct	*kf_tasks[2];	/* see SCX_CALL_OP_TASK() */

	atomic_long_t		ops_state;

kernel/sched/ext.c

+13 −0
Original line number Diff line number Diff line
@@ -1444,6 +1444,11 @@ static struct task_struct *scx_task_iter_next_locked(struct scx_task_iter *iter) 
 * Collection of event counters. Event types are placed in descending order.

 */

struct scx_event_stats {

	/*

	 * If ops.select_cpu() returns a CPU which can't be used by the task,

	 * the core scheduler code silently picks a fallback CPU.

	 */

	u64		SCX_EV_SELECT_CPU_FALLBACK;

};



/*
@@ -2170,6 +2175,10 @@ static void enqueue_task_scx(struct rq *rq, struct task_struct *p, int enq_flags 
	do_enqueue_task(rq, p, enq_flags, sticky_cpu);

out:

	rq->scx.flags &= ~SCX_RQ_IN_WAKEUP;



	if ((enq_flags & SCX_ENQ_CPU_SELECTED) &&

	    unlikely(cpu_of(rq) != p->scx.selected_cpu))

		__scx_add_event(SCX_EV_SELECT_CPU_FALLBACK, 1);

}



static void ops_dequeue(struct task_struct *p, u64 deq_flags)
@@ -3240,6 +3249,7 @@ static int select_task_rq_scx(struct task_struct *p, int prev_cpu, int wake_flag 


		cpu = SCX_CALL_OP_TASK_RET(SCX_KF_ENQUEUE | SCX_KF_SELECT_CPU,

					   select_cpu, p, prev_cpu, wake_flags);

		p->scx.selected_cpu = cpu;

		*ddsp_taskp = NULL;

		if (ops_cpu_valid(cpu, "from ops.select_cpu()"))

			return cpu;
@@ -3250,6 +3260,7 @@ static int select_task_rq_scx(struct task_struct *p, int prev_cpu, int wake_flag 
		s32 cpu;



		cpu = scx_select_cpu_dfl(p, prev_cpu, wake_flags, &found);

		p->scx.selected_cpu = cpu;

		if (found) {

			p->scx.slice = SCX_SLICE_DFL;

			p->scx.ddsp_dsq_id = SCX_DSQ_LOCAL;
@@ -4957,6 +4968,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len) 
	dump_line(&s, "--------------");



	scx_bpf_events(&events, sizeof(events));

	scx_dump_event(s, &events, SCX_EV_SELECT_CPU_FALLBACK);



	if (seq_buf_has_overflowed(&s) && dump_len >= sizeof(trunc_marker))

		memcpy(ei->dump + dump_len - sizeof(trunc_marker),
@@ -7090,6 +7102,7 @@ __bpf_kfunc void scx_bpf_events(struct scx_event_stats *events, 
	memset(&e_sys, 0, sizeof(e_sys));

	for_each_possible_cpu(cpu) {

		e_cpu = per_cpu_ptr(&event_stats_cpu, cpu);

		scx_agg_event(&e_sys, e_cpu, SCX_EV_SELECT_CPU_FALLBACK);

	}



	/*