[PATCH] mm: compaction: Trace compaction begin and end v2

[Mel Gorman]

Changelog since V1
o Print output parameters in pfn order			(vbabka)

This patch adds two tracepoints for compaction begin and end of a zone. Using
this it is possible to calculate how much time a workload is spending
within compaction and potentially debug problems related to cached pfns
for scanning. In combination with the direct reclaim and slab trace points
it should be possible to estimate most allocation-related overhead for
a workload.

Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
---
 include/trace/events/compaction.h | 42 +++++++++++++++++++++++++++++++++++++++
 mm/compaction.c                   |  4 ++++
 2 files changed, 46 insertions(+)

diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
index fde1b3e..06f544e 100644
--- a/include/trace/events/compaction.h
+++ b/include/trace/events/compaction.h
@@ -67,6 +67,48 @@ TRACE_EVENT(mm_compaction_migratepages,
 		__entry->nr_failed)
 );
 
+TRACE_EVENT(mm_compaction_begin,
+	TP_PROTO(unsigned long zone_start, unsigned long migrate_start,
+		unsigned long free_start, unsigned long zone_end),
+
+	TP_ARGS(zone_start, migrate_start, free_start, zone_end),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, zone_start)
+		__field(unsigned long, migrate_start)
+		__field(unsigned long, free_start)
+		__field(unsigned long, zone_end)
+	),
+
+	TP_fast_assign(
+		__entry->zone_start = zone_start;
+		__entry->migrate_start = migrate_start;
+		__entry->free_start = free_start;
+		__entry->zone_end = zone_end;
+	),
+
+	TP_printk("zone_start=%lu migrate_start=%lu free_start=%lu zone_end=%lu",
+		__entry->zone_start,
+		__entry->migrate_start,
+		__entry->free_start,
+		__entry->zone_end)
+);
+
+TRACE_EVENT(mm_compaction_end,
+	TP_PROTO(int status),
+
+	TP_ARGS(status),
+
+	TP_STRUCT__entry(
+		__field(int, status)
+	),
+
+	TP_fast_assign(
+		__entry->status = status;
+	),
+
+	TP_printk("status=%d", __entry->status)
+);
 
 #endif /* _TRACE_COMPACTION_H */
 
diff --git a/mm/compaction.c b/mm/compaction.c
index 805165b..bb50fd3 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -966,6 +966,8 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
 	if (compaction_restarting(zone, cc->order) && !current_is_kswapd())
 		__reset_isolation_suitable(zone);
 
+	trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, cc->free_pfn, end_pfn);
+
 	migrate_prep_local();
 
 	while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
@@ -1011,6 +1013,8 @@ out:
 	cc->nr_freepages -= release_freepages(&cc->freepages);
 	VM_BUG_ON(cc->nr_freepages != 0);
 
+	trace_mm_compaction_end(ret);
+
 	return ret;
 }
 
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