[PATCH 1/2] memcg: add memcg flush tracepoint event

[JP Kobryn <inwardvessel@xxxxxxxxx>]

This is a tracepoint event that contains the memcg pointer and an enum value
representing the reason associated with the flush.

Signed-off-by: JP Kobryn <inwardvessel@xxxxxxxxx>
---
 include/trace/events/memcg.h | 56 ++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/include/trace/events/memcg.h b/include/trace/events/memcg.h
index 8667e57816d2..9cccf0f13d4f 100644
--- a/include/trace/events/memcg.h
+++ b/include/trace/events/memcg.h
@@ -8,6 +8,43 @@
 #include <linux/memcontrol.h>
 #include <linux/tracepoint.h>
 
+#define MEMCG_FLUSH_REASONS \
+	EM(TRACE_MEMCG_FLUSH_READER, "reader") \
+	EM(TRACE_MEMCG_FLUSH_READER_SKIP, "reader skip") \
+	EM(TRACE_MEMCG_FLUSH_PERIODIC, "periodic") \
+	EMe(TRACE_MEMCG_FLUSH_ZSWAP, "zswap")
+
+#ifndef __MEMCG_DECLARE_TRACE_ENUMS_ONLY_ONCE
+#define __MEMCG_DECLARE_TRACE_ENUMS_ONLY_ONCE
+
+/* Redefine macros to help declare enum */
+#undef EM
+#undef EMe
+#define EM(a, b)	a,
+#define EMe(a, b)	a
+
+enum memcg_flush_reason {
+	MEMCG_FLUSH_REASONS
+};
+
+#endif /* __MEMCG_DECLARE_TRACE_ENUMS_ONLY_ONCE */
+
+/* Redefine macros to export the enums to userspace */
+#undef EM
+#undef EMe
+#define EM(a, b)	TRACE_DEFINE_ENUM(a);
+#define EMe(a, b)	TRACE_DEFINE_ENUM(a)
+
+MEMCG_FLUSH_REASONS;
+
+/*
+ * Redefine macros to map the enums to the strings that will
+ * be printed in the output
+ */
+#undef EM
+#undef EMe
+#define EM(a, b)	{ a, b },
+#define EMe(a, b)	{ a, b }
 
 DECLARE_EVENT_CLASS(memcg_rstat_stats,
 
@@ -74,6 +111,25 @@ DEFINE_EVENT(memcg_rstat_events, count_memcg_events,
 	TP_ARGS(memcg, item, val)
 );
 
+TRACE_EVENT(memcg_flush_stats,
+
+	TP_PROTO(struct mem_cgroup *memcg, enum memcg_flush_reason reason),
+
+	TP_ARGS(memcg, reason),
+
+	TP_STRUCT__entry(
+		__field(u64, id)
+		__field(enum memcg_flush_reason, reason)
+	),
+
+	TP_fast_assign(
+		__entry->id = cgroup_id(memcg->css.cgroup);
+		__entry->reason = reason;
+	),
+
+	TP_printk("memcg_id=%llu reason=%s",
+		  __entry->id, __print_symbolic(__entry->reason, MEMCG_FLUSH_REASONS))
+);
 
 #endif /* _TRACE_MEMCG_H */
 
-- 
2.47.0