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

[Mel Gorman <mgorman@suse.de>]

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@suse.de>
---
 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..f4e115a 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 zone_end, unsigned long free_start),
+
+	TP_ARGS(zone_start, migrate_start, zone_end, free_start),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, zone_start)
+		__field(unsigned long, migrate_start)
+		__field(unsigned long, zone_end)
+		__field(unsigned long, free_start)
+	),
+
+	TP_fast_assign(
+		__entry->zone_start = zone_start;
+		__entry->migrate_start = migrate_start;
+		__entry->zone_end = zone_end;
+		__entry->free_start = free_start;
+	),
+
+	TP_printk("zone_start=%lu migrate_start=%lu zone_end=%lu free_start=%lu",
+		__entry->zone_start,
+		__entry->migrate_start,
+		__entry->zone_end,
+		__entry->free_start)
+);
+
+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 c437893..78ff866 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -960,6 +960,8 @@ 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, end_pfn, cc->free_pfn);
+
 	migrate_prep_local();
 
 	while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
@@ -1005,6 +1007,8 @@ out:
 	cc->nr_freepages -= release_freepages(&cc->freepages);
 	VM_BUG_ON(cc->nr_freepages != 0);
 
+	trace_mm_compaction_end(ret);
+
 	return ret;
 }
 
-- 
Mel Gorman
SUSE Labs

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