[RFC][PATCH] memcg: malloc memory for possible node in hotplug

[Bob Liu <lliubbo@gmail.com>]

Current struct mem_cgroup_per_node and struct mem_cgroup_tree_per_node are
malloced for all possible node during system boot.

This may cause some memory waste, better if move it to memory hotplug.

Signed-off-by: Bob Liu <lliubbo@gmail.com>
---
 mm/memcontrol.c |   89 +++++++++++++++++++++++++++++++++++++++++-------------
 1 files changed, 67 insertions(+), 22 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a3d0420..a7a906b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -570,7 +570,7 @@ static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
 	struct mem_cgroup_per_zone *mz;
 	struct mem_cgroup_tree_per_zone *mctz;
 
-	for_each_node(node) {
+	for_each_node_state(nid, N_NORMAL_MEMORY) {
 		for (zone = 0; zone < MAX_NR_ZONES; zone++) {
 			mz = mem_cgroup_zoneinfo(memcg, node, zone);
 			mctz = soft_limit_tree_node_zone(node, zone);
@@ -4894,18 +4894,9 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
 	struct mem_cgroup_per_node *pn;
 	struct mem_cgroup_per_zone *mz;
 	enum lru_list l;
-	int zone, tmp = node;
-	/*
-	 * This routine is called against possible nodes.
-	 * But it's BUG to call kmalloc() against offline node.
-	 *
-	 * TODO: this routine can waste much memory for nodes which will
-	 *       never be onlined. It's better to use memory hotplug callback
-	 *       function.
-	 */
-	if (!node_state(node, N_NORMAL_MEMORY))
-		tmp = -1;
-	pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
+	int zone;
+
+	pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, node);
 	if (!pn)
 		return 1;
 
@@ -4972,7 +4963,7 @@ static void __mem_cgroup_free(struct mem_cgroup *memcg)
 	mem_cgroup_remove_from_trees(memcg);
 	free_css_id(&mem_cgroup_subsys, &memcg->css);
 
-	for_each_node(node)
+	for_each_node_state(nid, N_NORMAL_MEMORY)
 		free_mem_cgroup_per_zone_info(memcg, node);
 
 	free_percpu(memcg->stat);
@@ -5025,17 +5016,70 @@ static void __init enable_swap_cgroup(void)
 }
 #endif
 
+#ifdef CONFIG_MEMORY_HOTPLUG
+static int __meminit memcg_mem_hotplug_callback(struct notifier_block *self,
+			       unsigned long action, void *arg)
+{
+	struct memory_notify *mn = arg;
+	struct mem_cgroup *iter;
+	struct mem_cgroup_tree_per_node *rtpn;
+	struct mem_cgroup_tree_per_zone *rtpz;
+	int ret = 0;
+	int nid = mn->status_change_nid;
+	int zone;
+
+	switch (action) {
+	case MEM_ONLINE:
+		if (nid != -1) {
+			for_each_mem_cgroup(iter){
+				ret = alloc_mem_cgroup_per_zone_info(iter, nid);
+				if (ret)
+					goto free_out;
+			}
+
+			rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, nid);
+			if (!rtpn)
+				goto free_out;
+
+			soft_limit_tree.rb_tree_per_node[nid] = rtpn;
+
+			for (zone = 0; zone < MAX_NR_ZONES; zone++) {
+				rtpz = &rtpn->rb_tree_per_zone[zone];
+				rtpz->rb_root = RB_ROOT;
+				spin_lock_init(&rtpz->lock);
+			}
+		}
+		break;
+	case MEM_OFFLINE:
+		if (nid != -1) {
+			rtpn = soft_limit_tree.rb_tree_per_node[nid];
+			if (rtpn) {
+				kfree(rtpn);
+				soft_limit_tree.rb_tree_per_node[nid] = NULL;
+			}
+			goto free_out;
+		}
+		break;
+	}
+
+out:
+	return notifier_from_errno(ret);
+
+free_out:
+	for_each_mem_cgroup(iter)
+		free_mem_cgroup_per_zone_info(iter, nid);
+	goto out;
+}
+#endif
+
 static int mem_cgroup_soft_limit_tree_init(void)
 {
 	struct mem_cgroup_tree_per_node *rtpn;
 	struct mem_cgroup_tree_per_zone *rtpz;
-	int tmp, node, zone;
+	int node, zone;
 
-	for_each_node(node) {
-		tmp = node;
-		if (!node_state(node, N_NORMAL_MEMORY))
-			tmp = -1;
-		rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp);
+	for_each_node_state(nid, N_NORMAL_MEMORY) {
+		rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, node);
 		if (!rtpn)
 			goto err_cleanup;
 
@@ -5050,7 +5094,7 @@ static int mem_cgroup_soft_limit_tree_init(void)
 	return 0;
 
 err_cleanup:
-	for_each_node(node) {
+	for_each_node_state(nid, N_NORMAL_MEMORY) {
 		if (!soft_limit_tree.rb_tree_per_node[node])
 			break;
 		kfree(soft_limit_tree.rb_tree_per_node[node]);
@@ -5071,7 +5115,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 	if (!memcg)
 		return ERR_PTR(error);
 
-	for_each_node(node)
+	for_each_node_state(nid, N_NORMAL_MEMORY)
 		if (alloc_mem_cgroup_per_zone_info(memcg, node))
 			goto free_out;
 
@@ -5119,6 +5163,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 	atomic_set(&memcg->refcnt, 1);
 	memcg->move_charge_at_immigrate = 0;
 	mutex_init(&memcg->thresholds_lock);
+	hotplug_memory_notifier(memcg_mem_hotplug_callback, 0);
 	return &memcg->css;
 free_out:
 	__mem_cgroup_free(memcg);
-- 
1.7.0.4


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