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sched_ext: Add an event, SCX_EV_SELECT_CPU_FALLBACK

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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: Changwoo Min <changwoo@igalia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Changwoo Min 2025-01-31 16:09:29 +09:00 committed by Tejun Heo
parent 17103b8504
commit f7f6142107
2 changed files with 14 additions and 0 deletions
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1
include/linux/sched/ext.h
View File

@ -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;

13
kernel/sched/ext.c
View File

@ -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);
}
/*