mm/damon: add trace event for effective size quota

Aim-oriented DAMOS quota auto-tuning is an important and recommended
feature for DAMOS users. Add a trace event for the observability of the
tuned quota and tuning itself.

[[e-mail]: initialize sidx in damos_trace_esz()]
Link: https://lkml.kernel.org/r/[e-mail]
[[e-mail]: make damos_esz unconditional trace event]
Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: SeongJae Park <[e-mail]>
Cc: "Masami Hiramatsu (Google)" <[e-mail]>
Cc: Mathieu Desnoyers <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Cc: kernel test robot <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/trace/events/damon.h

···
 #include <linux/types.h>
 #include <linux/tracepoint.h>
 
+TRACE_EVENT(damos_esz,
+
+	TP_PROTO(unsigned int context_idx, unsigned int scheme_idx,
+		unsigned long esz),
+
+	TP_ARGS(context_idx, scheme_idx, esz),
+
+	TP_STRUCT__entry(
+		__field(unsigned int, context_idx)
+		__field(unsigned int, scheme_idx)
+		__field(unsigned long, esz)
+	),
+
+	TP_fast_assign(
+		__entry->context_idx = context_idx;
+		__entry->scheme_idx = scheme_idx;
+		__entry->esz = esz;
+	),
+
+	TP_printk("ctx_idx=%u scheme_idx=%u esz=%lu",
+			__entry->context_idx, __entry->scheme_idx,
+			__entry->esz)
+);
+
 TRACE_EVENT_CONDITION(damos_before_apply,
 
 	TP_PROTO(unsigned int context_idx, unsigned int scheme_idx,

mm/damon/core.c

···
 	quota->esz = esz;
 }
 
+static void damos_trace_esz(struct damon_ctx *c, struct damos *s,
+		struct damos_quota *quota)
+{
+	unsigned int cidx = 0, sidx = 0;
+	struct damos *siter;
+
+	damon_for_each_scheme(siter, c) {
+		if (siter == s)
+			break;
+		sidx++;
+	}
+	trace_damos_esz(cidx, sidx, quota->esz);
+}
+
 static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
 {
 	struct damos_quota *quota = &s->quota;
 	struct damon_target *t;
 	struct damon_region *r;
-	unsigned long cumulated_sz;
+	unsigned long cumulated_sz, cached_esz;
 	unsigned int score, max_score = 0;
 
 	if (!quota->ms && !quota->sz && list_empty(&quota->goals))
···
 		quota->total_charged_sz += quota->charged_sz;
 		quota->charged_from = jiffies;
 		quota->charged_sz = 0;
+		if (trace_damos_esz_enabled())
+			cached_esz = quota->esz;
 		damos_set_effective_quota(quota);
+		if (trace_damos_esz_enabled() && quota->esz != cached_esz)
+			damos_trace_esz(c, s, quota);
 	}
 
 	if (!c->ops.get_scheme_score)