sched_ext: Add an event, SCX_EV_ENQ_SKIP_EXITING

Add a core event, SCX_EV_ENQ_SKIP_EXITING, which represents how many
times a task is enqueued to a local DSQ when exiting if
SCX_OPS_ENQ_EXITING is not set.

__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>

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index cbb3d059072fb649eccd737dc30125fb28fd338a..c72ba405a1d38a082ab48e7ba273b8a5b0572b3d 100644 (file)
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -1461,6 +1461,12 @@ struct scx_event_stats {
         * continued to run because there were no other tasks on the CPU.
         */
        u64             SCX_EV_DISPATCH_KEEP_LAST;
+
+       /*
+        * If SCX_OPS_ENQ_EXITING is not set, the number of times that a task
+        * is dispatched to a local DSQ when exiting.
+        */
+       u64             SCX_EV_ENQ_SKIP_EXITING;
 };
 
 /*
@@ -2068,8 +2074,10 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
 
        /* see %SCX_OPS_ENQ_EXITING */
        if (!static_branch_unlikely(&scx_ops_enq_exiting) &&
-           unlikely(p->flags & PF_EXITING))
+           unlikely(p->flags & PF_EXITING)) {
+               __scx_add_event(SCX_EV_ENQ_SKIP_EXITING, 1);
                goto local;
+       }
 
        if (!SCX_HAS_OP(enqueue))
                goto global;
@@ -4985,6 +4993,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
        scx_dump_event(s, &events, SCX_EV_SELECT_CPU_FALLBACK);
        scx_dump_event(s, &events, SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE);
        scx_dump_event(s, &events, SCX_EV_DISPATCH_KEEP_LAST);
+       scx_dump_event(s, &events, SCX_EV_ENQ_SKIP_EXITING);
 
        if (seq_buf_has_overflowed(&s) && dump_len >= sizeof(trunc_marker))
                memcpy(ei->dump + dump_len - sizeof(trunc_marker),
@@ -7121,6 +7130,7 @@ __bpf_kfunc void scx_bpf_events(struct scx_event_stats *events,
                scx_agg_event(&e_sys, e_cpu, SCX_EV_SELECT_CPU_FALLBACK);
                scx_agg_event(&e_sys, e_cpu, SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE);
                scx_agg_event(&e_sys, e_cpu, SCX_EV_DISPATCH_KEEP_LAST);
+               scx_agg_event(&e_sys, e_cpu, SCX_EV_ENQ_SKIP_EXITING);
        }
 
        /*