[PATCH V3 6/7] Enable per-memcg background reclaim.

[Ying Han <yinghan@xxxxxxxxxx>]

By default the per-memcg background reclaim is disabled when the limit_in_bytes
is set the maximum or the wmark_ratio is 0. The kswapd_run() is called when the
memcg is being resized, and kswapd_stop() is called when the memcg is being
deleted.

The per-memcg kswapd is waked up based on the usage and low_wmark, which is
checked once per 1024 increments per cpu. The memcg's kswapd is waked up if the
usage is larger than the low_wmark.

changelog v3..v2:
1. some clean-ups

changelog v2..v1:
1. start/stop the per-cgroup kswapd at create/delete cgroup stage.
2. remove checking the wmark from per-page charging. now it checks the wmark
periodically based on the event counter.

Signed-off-by: Ying Han <yinghan@xxxxxxxxxx>
---
 mm/memcontrol.c |   37 +++++++++++++++++++++++++++++++++++++
 1 files changed, 37 insertions(+), 0 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index efeade3..bfa8646 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -105,10 +105,12 @@ enum mem_cgroup_events_index {
 enum mem_cgroup_events_target {
 	MEM_CGROUP_TARGET_THRESH,
 	MEM_CGROUP_TARGET_SOFTLIMIT,
+	MEM_CGROUP_WMARK_EVENTS_THRESH,
 	MEM_CGROUP_NTARGETS,
 };
 #define THRESHOLDS_EVENTS_TARGET (128)
 #define SOFTLIMIT_EVENTS_TARGET (1024)
+#define WMARK_EVENTS_TARGET (1024)
 
 struct mem_cgroup_stat_cpu {
 	long count[MEM_CGROUP_STAT_NSTATS];
@@ -366,6 +368,7 @@ static void mem_cgroup_put(struct mem_cgroup *mem);
 static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
 static void drain_all_stock_async(void);
 static unsigned long get_wmark_ratio(struct mem_cgroup *mem);
+static void wake_memcg_kswapd(struct mem_cgroup *mem);
 
 static struct mem_cgroup_per_zone *
 mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
@@ -545,6 +548,12 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
 	return mz;
 }
 
+static void mem_cgroup_check_wmark(struct mem_cgroup *mem)
+{
+	if (!mem_cgroup_watermark_ok(mem, CHARGE_WMARK_LOW))
+		wake_memcg_kswapd(mem);
+}
+
 /*
  * Implementation Note: reading percpu statistics for memcg.
  *
@@ -675,6 +684,9 @@ static void __mem_cgroup_target_update(struct mem_cgroup *mem, int target)
 	case MEM_CGROUP_TARGET_SOFTLIMIT:
 		next = val + SOFTLIMIT_EVENTS_TARGET;
 		break;
+	case MEM_CGROUP_WMARK_EVENTS_THRESH:
+		next = val + WMARK_EVENTS_TARGET;
+		break;
 	default:
 		return;
 	}
@@ -698,6 +710,10 @@ static void memcg_check_events(struct mem_cgroup *mem, struct page *page)
 			__mem_cgroup_target_update(mem,
 				MEM_CGROUP_TARGET_SOFTLIMIT);
 		}
+		if (unlikely(__memcg_event_check(mem,
+			MEM_CGROUP_WMARK_EVENTS_THRESH))){
+			mem_cgroup_check_wmark(mem);
+		}
 	}
 }
 
@@ -3384,6 +3400,10 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
 	if (!ret && enlarge)
 		memcg_oom_recover(memcg);
 
+	if (!mem_cgroup_is_root(memcg) && !memcg->kswapd_wait &&
+			memcg->wmark_ratio)
+		kswapd_run(0, memcg);
+
 	return ret;
 }
 
@@ -4680,6 +4700,7 @@ static void __mem_cgroup_free(struct mem_cgroup *mem)
 {
 	int node;
 
+	kswapd_stop(0, mem);
 	mem_cgroup_remove_from_trees(mem);
 	free_css_id(&mem_cgroup_subsys, &mem->css);
 
@@ -4786,6 +4807,22 @@ int mem_cgroup_last_scanned_node(struct mem_cgroup *mem)
 	return mem->last_scanned_node;
 }
 
+static inline
+void wake_memcg_kswapd(struct mem_cgroup *mem)
+{
+	wait_queue_head_t *wait;
+
+	if (!mem || !mem->wmark_ratio)
+		return;
+
+	wait = mem->kswapd_wait;
+
+	if (!wait || !waitqueue_active(wait))
+		return;
+
+	wake_up_interruptible(wait);
+}
+
 static int mem_cgroup_soft_limit_tree_init(void)
 {
 	struct mem_cgroup_tree_per_node *rtpn;
-- 
1.7.3.1

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