vmscan: tracing: add trace events for LRU page isolation

Add an event for when pages are isolated en-masse from the LRU lists.
This event augments the information available on LRU traffic and can be
used to evaluate lumpy reclaim.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Acked-by: NRik van Riel <riel@redhat.com>
Acked-by: NLarry Woodman <lwoodman@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/trace/events/vmscan.h

@@ -109,6 +109,52 @@ TRACE_EVENT(mm_vmscan_direct_reclaim_end,
 	TP_printk("nr_reclaimed=%lu", __entry->nr_reclaimed)
 );
 
+TRACE_EVENT(mm_vmscan_lru_isolate,
+
+	TP_PROTO(int order,
+		unsigned long nr_requested,
+		unsigned long nr_scanned,
+		unsigned long nr_taken,
+		unsigned long nr_lumpy_taken,
+		unsigned long nr_lumpy_dirty,
+		unsigned long nr_lumpy_failed,
+		int isolate_mode),
+
+	TP_ARGS(order, nr_requested, nr_scanned, nr_taken, nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, isolate_mode),
+
+	TP_STRUCT__entry(
+		__field(int, order)
+		__field(unsigned long, nr_requested)
+		__field(unsigned long, nr_scanned)
+		__field(unsigned long, nr_taken)
+		__field(unsigned long, nr_lumpy_taken)
+		__field(unsigned long, nr_lumpy_dirty)
+		__field(unsigned long, nr_lumpy_failed)
+		__field(int, isolate_mode)
+	),
+
+	TP_fast_assign(
+		__entry->order = order;
+		__entry->nr_requested = nr_requested;
+		__entry->nr_scanned = nr_scanned;
+		__entry->nr_taken = nr_taken;
+		__entry->nr_lumpy_taken = nr_lumpy_taken;
+		__entry->nr_lumpy_dirty = nr_lumpy_dirty;
+		__entry->nr_lumpy_failed = nr_lumpy_failed;
+		__entry->isolate_mode = isolate_mode;
+	),
+
+	TP_printk("isolate_mode=%d order=%d nr_requested=%lu nr_scanned=%lu nr_taken=%lu contig_taken=%lu contig_dirty=%lu contig_failed=%lu",
+		__entry->isolate_mode,
+		__entry->order,
+		__entry->nr_requested,
+		__entry->nr_scanned,
+		__entry->nr_taken,
+		__entry->nr_lumpy_taken,
+		__entry->nr_lumpy_dirty,
+		__entry->nr_lumpy_failed)
+);
+
 #endif /* _TRACE_VMSCAN_H */
 
 /* This part must be outside protection */

mm/vmscan.c

@@ -919,6 +919,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 		unsigned long *scanned, int order, int mode, int file)
 {
 	unsigned long nr_taken = 0;
+	unsigned long nr_lumpy_taken = 0;
+	unsigned long nr_lumpy_dirty = 0;
+	unsigned long nr_lumpy_failed = 0;
 	unsigned long scan;
 
 	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
@@ -996,12 +999,25 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 				list_move(&cursor_page->lru, dst);
 				mem_cgroup_del_lru(cursor_page);
 				nr_taken++;
+				nr_lumpy_taken++;
+				if (PageDirty(cursor_page))
+					nr_lumpy_dirty++;
 				scan++;
+			} else {
+				if (mode == ISOLATE_BOTH &&
+						page_count(cursor_page))
+					nr_lumpy_failed++;
 			}
 		}
 	}
 
 	*scanned = scan;
+
+	trace_mm_vmscan_lru_isolate(order,
+			nr_to_scan, scan,
+			nr_taken,
+			nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
+			mode);
 	return nr_taken;
 }