[PATCH v2] mm: vmscan: add tracepoints for node reclaim

[Yafang Shao <laoar.shao@gmail.com>]

In the page alloc fast path, it may do node reclaim, which may cause
latency spike.
We should add tracepoint for this event, and also measure the latency
it causes.

So bellow two tracepoints are introduced,
	mm_vmscan_node_reclaim_begin
	mm_vmscan_node_reclaim_end

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/trace/events/vmscan.h | 32 ++++++++++++++++++++++++++++++++
 mm/vmscan.c                   |  6 ++++++
 2 files changed, 38 insertions(+)

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index a1cb913..c1ddf28 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -465,6 +465,38 @@
 		__entry->ratio,
 		show_reclaim_flags(__entry->reclaim_flags))
 );
+
+TRACE_EVENT(mm_vmscan_node_reclaim_begin,
+
+	TP_PROTO(int nid, int order, gfp_t gfp_flags),
+
+	TP_ARGS(nid, order, gfp_flags),
+
+	TP_STRUCT__entry(
+		__field(int, nid)
+		__field(int, order)
+		__field(gfp_t, gfp_flags)
+	),
+
+	TP_fast_assign(
+		__entry->nid = nid;
+		__entry->order = order;
+		__entry->gfp_flags = gfp_flags;
+	),
+
+	TP_printk("nid=%d order=%d gfp_flags=%s",
+		__entry->nid,
+		__entry->order,
+		show_gfp_flags(__entry->gfp_flags))
+);
+
+DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_node_reclaim_end,
+
+	TP_PROTO(unsigned long nr_reclaimed),
+
+	TP_ARGS(nr_reclaimed)
+);
+
 #endif /* _TRACE_VMSCAN_H */
 
 /* This part must be outside protection */
diff --git a/mm/vmscan.c b/mm/vmscan.c
index ac4806f..2bee5d1 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4241,6 +4241,9 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
 		.reclaim_idx = gfp_zone(gfp_mask),
 	};
 
+	trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
+					   sc.gfp_mask);
+
 	cond_resched();
 	fs_reclaim_acquire(sc.gfp_mask);
 	/*
@@ -4267,6 +4270,9 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
 	current->flags &= ~PF_SWAPWRITE;
 	memalloc_noreclaim_restore(noreclaim_flag);
 	fs_reclaim_release(sc.gfp_mask);
+
+	trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
+
 	return sc.nr_reclaimed >= nr_pages;
 }
 
-- 
1.8.3.1