[PATCH v2 1/2] mm/compaction: keep compaction deferral state per migration mode

[Qiliang Yuan]

A zone keeps one compaction deferral state, compact_considered,
compact_defer_shift and compact_order_failed, for all migration modes.
Only sync compaction failures defer a zone, so a failed async direct
compaction is never deferred.

Deferring async compaction on that shared state would defer sync
compaction along with it, though sync compaction can still succeed on
the pageblocks async compaction skips.

Turn the three fields into arrays indexed by sync, like
compact_cached_migrate_pfn, and pass the mode to the deferral helpers.
All callers use the sync state for now, and a reset clears both. Add a
sync field to the deferral tracepoints, and emit
mm_compaction_defer_reset once for each state a reset clears.

Signed-off-by: Qiliang Yuan <odys.yuan@xxxxxxxxx>
---
 include/linux/mmzone.h            |  7 +++--
 include/trace/events/compaction.h | 27 +++++++++--------
 mm/compaction.c                   | 62 +++++++++++++++++++++------------------
 3 files changed, 52 insertions(+), 44 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index ecd1ebd49756c..73da870fff975 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1150,10 +1150,11 @@ struct zone {
 	 * are skipped before trying again. The number attempted since
 	 * last failure is tracked with compact_considered.
 	 * compact_order_failed is the minimum compaction failed order.
+	 * Indexed by sync, like compact_cached_migrate_pfn.
 	 */
-	unsigned int		compact_considered;
-	unsigned int		compact_defer_shift;
-	int			compact_order_failed;
+	unsigned int		compact_considered[ASYNC_AND_SYNC];
+	unsigned int		compact_defer_shift[ASYNC_AND_SYNC];
+	int			compact_order_failed[ASYNC_AND_SYNC];
 #endif
 
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
index d05759d185389..23ac6e1750623 100644
--- a/include/trace/events/compaction.h
+++ b/include/trace/events/compaction.h
@@ -238,14 +238,15 @@ DEFINE_EVENT(mm_compaction_suitable_template, mm_compaction_suitable,
 
 DECLARE_EVENT_CLASS(mm_compaction_defer_template,
 
-	TP_PROTO(struct zone *zone, int order),
+	TP_PROTO(struct zone *zone, int order, bool sync),
 
-	TP_ARGS(zone, order),
+	TP_ARGS(zone, order, sync),
 
 	TP_STRUCT__entry(
 		__field(int, nid)
 		__field(enum zone_type, idx)
 		__field(int, order)
+		__field(bool, sync)
 		__field(unsigned int, considered)
 		__field(unsigned int, defer_shift)
 		__field(int, order_failed)
@@ -255,15 +256,17 @@ DECLARE_EVENT_CLASS(mm_compaction_defer_template,
 		__entry->nid = zone_to_nid(zone);
 		__entry->idx = zone_idx(zone);
 		__entry->order = order;
-		__entry->considered = zone->compact_considered;
-		__entry->defer_shift = zone->compact_defer_shift;
-		__entry->order_failed = zone->compact_order_failed;
+		__entry->sync = sync;
+		__entry->considered = zone->compact_considered[sync];
+		__entry->defer_shift = zone->compact_defer_shift[sync];
+		__entry->order_failed = zone->compact_order_failed[sync];
 	),
 
-	TP_printk("node=%d zone=%-8s order=%d order_failed=%d consider=%u limit=%lu",
+	TP_printk("node=%d zone=%-8s order=%d sync=%d order_failed=%d consider=%u limit=%lu",
 		__entry->nid,
 		__print_symbolic(__entry->idx, ZONE_TYPE),
 		__entry->order,
+		__entry->sync,
 		__entry->order_failed,
 		__entry->considered,
 		1UL << __entry->defer_shift)
@@ -271,23 +274,23 @@ DECLARE_EVENT_CLASS(mm_compaction_defer_template,
 
 DEFINE_EVENT(mm_compaction_defer_template, mm_compaction_deferred,
 
-	TP_PROTO(struct zone *zone, int order),
+	TP_PROTO(struct zone *zone, int order, bool sync),
 
-	TP_ARGS(zone, order)
+	TP_ARGS(zone, order, sync)
 );
 
 DEFINE_EVENT(mm_compaction_defer_template, mm_compaction_defer_compaction,
 
-	TP_PROTO(struct zone *zone, int order),
+	TP_PROTO(struct zone *zone, int order, bool sync),
 
-	TP_ARGS(zone, order)
+	TP_ARGS(zone, order, sync)
 );
 
 DEFINE_EVENT(mm_compaction_defer_template, mm_compaction_defer_reset,
 
-	TP_PROTO(struct zone *zone, int order),
+	TP_PROTO(struct zone *zone, int order, bool sync),
 
-	TP_ARGS(zone, order)
+	TP_ARGS(zone, order, sync)
 );
 
 TRACE_EVENT(mm_compaction_kcompactd_sleep,
diff --git a/mm/compaction.c b/mm/compaction.c
index f1b2060eb2016..e7a450b2be757 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -124,35 +124,35 @@ static unsigned long release_free_list(struct list_head *freepages)
  * allocation success. 1 << compact_defer_shift, compactions are skipped up
  * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
  */
-static void defer_compaction(struct zone *zone, int order)
+static void defer_compaction(struct zone *zone, int order, bool sync)
 {
-	zone->compact_considered = 0;
-	zone->compact_defer_shift++;
+	zone->compact_considered[sync] = 0;
+	zone->compact_defer_shift[sync]++;
 
-	if (order < zone->compact_order_failed)
-		zone->compact_order_failed = order;
+	if (order < zone->compact_order_failed[sync])
+		zone->compact_order_failed[sync] = order;
 
-	if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
-		zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
+	if (zone->compact_defer_shift[sync] > COMPACT_MAX_DEFER_SHIFT)
+		zone->compact_defer_shift[sync] = COMPACT_MAX_DEFER_SHIFT;
 
-	trace_mm_compaction_defer_compaction(zone, order);
+	trace_mm_compaction_defer_compaction(zone, order, sync);
 }
 
 /* Returns true if compaction should be skipped this time */
-static bool compaction_deferred(struct zone *zone, int order)
+static bool compaction_deferred(struct zone *zone, int order, bool sync)
 {
-	unsigned long defer_limit = 1UL << zone->compact_defer_shift;
+	unsigned long defer_limit = 1UL << zone->compact_defer_shift[sync];
 
-	if (order < zone->compact_order_failed)
+	if (order < zone->compact_order_failed[sync])
 		return false;
 
 	/* Avoid possible overflow */
-	if (++zone->compact_considered >= defer_limit) {
-		zone->compact_considered = defer_limit;
+	if (++zone->compact_considered[sync] >= defer_limit) {
+		zone->compact_considered[sync] = defer_limit;
 		return false;
 	}
 
-	trace_mm_compaction_deferred(zone, order);
+	trace_mm_compaction_deferred(zone, order, sync);
 
 	return true;
 }
@@ -165,24 +165,28 @@ static bool compaction_deferred(struct zone *zone, int order)
 void compaction_defer_reset(struct zone *zone, int order,
 		bool alloc_success)
 {
-	if (alloc_success) {
-		zone->compact_considered = 0;
-		zone->compact_defer_shift = 0;
-	}
-	if (order >= zone->compact_order_failed)
-		zone->compact_order_failed = order + 1;
+	int sync;
+
+	for (sync = 0; sync < ASYNC_AND_SYNC; sync++) {
+		if (alloc_success) {
+			zone->compact_considered[sync] = 0;
+			zone->compact_defer_shift[sync] = 0;
+		}
+		if (order >= zone->compact_order_failed[sync])
+			zone->compact_order_failed[sync] = order + 1;
 
-	trace_mm_compaction_defer_reset(zone, order);
+		trace_mm_compaction_defer_reset(zone, order, sync);
+	}
 }
 
-/* Returns true if restarting compaction after many failures */
+/* Return true if restarting sync compaction after many failures */
 static bool compaction_restarting(struct zone *zone, int order)
 {
-	if (order < zone->compact_order_failed)
+	if (order < zone->compact_order_failed[true])
 		return false;
 
-	return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
-		zone->compact_considered >= 1UL << zone->compact_defer_shift;
+	return zone->compact_defer_shift[true] == COMPACT_MAX_DEFER_SHIFT &&
+		zone->compact_considered[true] >= 1UL << zone->compact_defer_shift[true];
 }
 
 /* Returns true if the pageblock should be scanned for pages to isolate. */
@@ -2855,7 +2859,7 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
 				continue;
 
 		if (prio > MIN_COMPACT_PRIORITY
-					&& compaction_deferred(zone, order)) {
+					&& compaction_deferred(zone, order, true)) {
 			rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
 			continue;
 		}
@@ -2893,7 +2897,7 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
 			 * so we defer compaction there. If it ends up
 			 * succeeding after all, it will be reset.
 			 */
-			defer_compaction(zone, order);
+			defer_compaction(zone, order, true);
 
 		/*
 		 * We might have stopped compacting due to need_resched() in
@@ -3111,7 +3115,7 @@ static void kcompactd_do_work(pg_data_t *pgdat)
 		if (!populated_zone(zone))
 			continue;
 
-		if (compaction_deferred(zone, cc.order))
+		if (compaction_deferred(zone, cc.order, true))
 			continue;
 
 		ret = compaction_suit_allocation_order(zone,
@@ -3141,7 +3145,7 @@ static void kcompactd_do_work(pg_data_t *pgdat)
 			 * We use sync migration mode here, so we defer like
 			 * sync direct compaction does.
 			 */
-			defer_compaction(zone, cc.order);
+			defer_compaction(zone, cc.order, true);
 		}
 
 		count_compact_events(KCOMPACTD_MIGRATE_SCANNED,

-- 
2.43.0