mm/compaction: more trace to understand when/why compaction start/finish

It is not well analyzed that when/why compaction start/finish or not.
With these new tracepoints, we can know much more about start/finish
reason of compaction. I can find following bug with these tracepoint.

http://www.spinics.net/lists/linux-mm/msg81582.html

Signed-off-by: Joonsoo Kim <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: David Rientjes <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/compaction.h

···
 #define COMPACT_PARTIAL		3
 /* The full zone was compacted */
 #define COMPACT_COMPLETE	4
+/* For more detailed tracepoint output */
+#define COMPACT_NO_SUITABLE_PAGE	5
+#define COMPACT_NOT_SUITABLE_ZONE	6
 /* When adding new state, please change compaction_status_string, too */
 
 /* Used to signal whether compaction detected need_sched() or lock contention */

include/trace/events/compaction.h

···
 		compaction_status_string[__entry->status])
 );
 
+TRACE_EVENT(mm_compaction_try_to_compact_pages,
+
+	TP_PROTO(
+		int order,
+		gfp_t gfp_mask,
+		enum migrate_mode mode),
+
+	TP_ARGS(order, gfp_mask, mode),
+
+	TP_STRUCT__entry(
+		__field(int, order)
+		__field(gfp_t, gfp_mask)
+		__field(enum migrate_mode, mode)
+	),
+
+	TP_fast_assign(
+		__entry->order = order;
+		__entry->gfp_mask = gfp_mask;
+		__entry->mode = mode;
+	),
+
+	TP_printk("order=%d gfp_mask=0x%x mode=%d",
+		__entry->order,
+		__entry->gfp_mask,
+		(int)__entry->mode)
+);
+
+DECLARE_EVENT_CLASS(mm_compaction_suitable_template,
+
+	TP_PROTO(struct zone *zone,
+		int order,
+		int ret),
+
+	TP_ARGS(zone, order, ret),
+
+	TP_STRUCT__entry(
+		__field(int, nid)
+		__field(char *, name)
+		__field(int, order)
+		__field(int, ret)
+	),
+
+	TP_fast_assign(
+		__entry->nid = zone_to_nid(zone);
+		__entry->name = (char *)zone->name;
+		__entry->order = order;
+		__entry->ret = ret;
+	),
+
+	TP_printk("node=%d zone=%-8s order=%d ret=%s",
+		__entry->nid,
+		__entry->name,
+		__entry->order,
+		compaction_status_string[__entry->ret])
+);
+
+DEFINE_EVENT(mm_compaction_suitable_template, mm_compaction_finished,
+
+	TP_PROTO(struct zone *zone,
+		int order,
+		int ret),
+
+	TP_ARGS(zone, order, ret)
+);
+
+DEFINE_EVENT(mm_compaction_suitable_template, mm_compaction_suitable,
+
+	TP_PROTO(struct zone *zone,
+		int order,
+		int ret),
+
+	TP_ARGS(zone, order, ret)
+);
+
 #endif /* _TRACE_COMPACTION_H */
 
 /* This part must be outside protection */

mm/compaction.c

···
 	"continue",
 	"partial",
 	"complete",
+	"no_suitable_page",
+	"not_suitable_zone",
 };
 #endif
 
···
 	return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
 }
 
-static int compact_finished(struct zone *zone, struct compact_control *cc,
+static int __compact_finished(struct zone *zone, struct compact_control *cc,
 			    const int migratetype)
 {
 	unsigned int order;
···
 			return COMPACT_PARTIAL;
 	}
 
-	return COMPACT_CONTINUE;
+	return COMPACT_NO_SUITABLE_PAGE;
+}
+
+static int compact_finished(struct zone *zone, struct compact_control *cc,
+			    const int migratetype)
+{
+	int ret;
+
+	ret = __compact_finished(zone, cc, migratetype);
+	trace_mm_compaction_finished(zone, cc->order, ret);
+	if (ret == COMPACT_NO_SUITABLE_PAGE)
+		ret = COMPACT_CONTINUE;
+
+	return ret;
 }
 
 /*
···
  *   COMPACT_PARTIAL  - If the allocation would succeed without compaction
  *   COMPACT_CONTINUE - If compaction should run now
  */
-unsigned long compaction_suitable(struct zone *zone, int order,
+static unsigned long __compaction_suitable(struct zone *zone, int order,
 					int alloc_flags, int classzone_idx)
 {
 	int fragindex;
···
 	 */
 	fragindex = fragmentation_index(zone, order);
 	if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
-		return COMPACT_SKIPPED;
+		return COMPACT_NOT_SUITABLE_ZONE;
 
 	return COMPACT_CONTINUE;
+}
+
+unsigned long compaction_suitable(struct zone *zone, int order,
+					int alloc_flags, int classzone_idx)
+{
+	unsigned long ret;
+
+	ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx);
+	trace_mm_compaction_suitable(zone, order, ret);
+	if (ret == COMPACT_NOT_SUITABLE_ZONE)
+		ret = COMPACT_SKIPPED;
+
+	return ret;
 }
 
 static int compact_zone(struct zone *zone, struct compact_control *cc)
···
 	/* Check if the GFP flags allow compaction */
 	if (!order || !may_enter_fs || !may_perform_io)
 		return COMPACT_SKIPPED;
+
+	trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode);
 
 	/* Compact each zone in the list */
 	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,