[PATCH 09/23] kmem slab accounting basic infrastructure

[Glauber Costa <glommer@parallels.com>]

This patch adds the basic infrastructure for the accounting of the slab
caches. To control that, the following files are created:

 * memory.kmem.usage_in_bytes
 * memory.kmem.limit_in_bytes
 * memory.kmem.failcnt
 * memory.kmem.max_usage_in_bytes

They have the same meaning of their user memory counterparts. They reflect
the state of the "kmem" res_counter.

The code is not enabled until a limit is set. This can be tested by the flag
"kmem_accounted". This means that after the patch is applied, no behavioral
changes exists for whoever is still using memcg to control their memory usage.

We always account to both user and kernel resource_counters. This effectively
means that an independent kernel limit is in place when the limit is set
to a lower value than the user memory. A equal or higher value means that the
user limit will always hit first, meaning that kmem is effectively unlimited.

People who want to track kernel memory but not limit it, can set this limit
to a very high number (like RESOURCE_MAX - 1page - that no one will ever hit,
or equal to the user memory)

Signed-off-by: Glauber Costa <glommer@parallels.com>
CC: Michal Hocko <mhocko@suse.cz>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
CC: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/memcontrol.c |   80 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 79 insertions(+), 1 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2810228..36f1e6b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -252,6 +252,10 @@ struct mem_cgroup {
 	};
 
 	/*
+	 * the counter to account for kernel memory usage.
+	 */
+	struct res_counter kmem;
+	/*
 	 * Per cgroup active and inactive list, similar to the
 	 * per zone LRU lists.
 	 */
@@ -266,6 +270,7 @@ struct mem_cgroup {
 	 * Should the accounting and control be hierarchical, per subtree?
 	 */
 	bool use_hierarchy;
+	bool kmem_accounted;
 
 	bool		oom_lock;
 	atomic_t	under_oom;
@@ -378,6 +383,7 @@ enum res_type {
 	_MEM,
 	_MEMSWAP,
 	_OOM_TYPE,
+	_KMEM,
 };
 
 #define MEMFILE_PRIVATE(x, val)	(((x) << 16) | (val))
@@ -1470,6 +1476,10 @@ done:
 		res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
 		res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
 		res_counter_read_u64(&memcg->memsw, RES_FAILCNT));
+	printk(KERN_INFO "kmem: usage %llukB, limit %llukB, failcnt %llu\n",
+		res_counter_read_u64(&memcg->kmem, RES_USAGE) >> 10,
+		res_counter_read_u64(&memcg->kmem, RES_LIMIT) >> 10,
+		res_counter_read_u64(&memcg->kmem, RES_FAILCNT));
 }
 
 /*
@@ -3914,6 +3924,11 @@ static ssize_t mem_cgroup_read(struct cgroup *cont, struct cftype *cft,
 		else
 			val = res_counter_read_u64(&memcg->memsw, name);
 		break;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+	case _KMEM:
+		val = res_counter_read_u64(&memcg->kmem, name);
+		break;
+#endif
 	default:
 		BUG();
 	}
@@ -3951,8 +3966,26 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
 			break;
 		if (type == _MEM)
 			ret = mem_cgroup_resize_limit(memcg, val);
-		else
+		else if (type == _MEMSWAP)
 			ret = mem_cgroup_resize_memsw_limit(memcg, val);
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+		else if (type == _KMEM) {
+			ret = res_counter_set_limit(&memcg->kmem, val);
+			if (ret)
+				break;
+			/*
+			 * Once enabled, can't be disabled. We could in theory
+			 * disable it if we haven't yet created any caches, or
+			 * if we can shrink them all to death.
+			 *
+			 * But it is not worth the trouble
+			 */
+			if (!memcg->kmem_accounted && val != RESOURCE_MAX)
+				memcg->kmem_accounted = true;
+		}
+#endif
+		else
+			return -EINVAL;
 		break;
 	case RES_SOFT_LIMIT:
 		ret = res_counter_memparse_write_strategy(buffer, &val);
@@ -4017,12 +4050,20 @@ static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
 	case RES_MAX_USAGE:
 		if (type == _MEM)
 			res_counter_reset_max(&memcg->res);
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+		else if (type == _KMEM)
+			res_counter_reset_max(&memcg->kmem);
+#endif
 		else
 			res_counter_reset_max(&memcg->memsw);
 		break;
 	case RES_FAILCNT:
 		if (type == _MEM)
 			res_counter_reset_failcnt(&memcg->res);
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+		else if (type == _KMEM)
+			res_counter_reset_failcnt(&memcg->kmem);
+#endif
 		else
 			res_counter_reset_failcnt(&memcg->memsw);
 		break;
@@ -4647,6 +4688,33 @@ static int mem_control_numa_stat_open(struct inode *unused, struct file *file)
 #endif /* CONFIG_NUMA */
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+static struct cftype kmem_cgroup_files[] = {
+	{
+		.name = "kmem.limit_in_bytes",
+		.private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
+		.write_string = mem_cgroup_write,
+		.read = mem_cgroup_read,
+	},
+	{
+		.name = "kmem.usage_in_bytes",
+		.private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
+		.read = mem_cgroup_read,
+	},
+	{
+		.name = "kmem.failcnt",
+		.private = MEMFILE_PRIVATE(_KMEM, RES_FAILCNT),
+		.trigger = mem_cgroup_reset,
+		.read = mem_cgroup_read,
+	},
+	{
+		.name = "kmem.max_usage_in_bytes",
+		.private = MEMFILE_PRIVATE(_KMEM, RES_MAX_USAGE),
+		.trigger = mem_cgroup_reset,
+		.read = mem_cgroup_read,
+	},
+	{},
+};
+
 static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
 	return mem_cgroup_sockets_init(memcg, ss);
@@ -4654,6 +4722,7 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 
 static void kmem_cgroup_destroy(struct mem_cgroup *memcg)
 {
+	BUG_ON(res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0);
 	mem_cgroup_sockets_destroy(memcg);
 }
 #else
@@ -4979,6 +5048,12 @@ mem_cgroup_create(struct cgroup *cont)
 		int cpu;
 		enable_swap_cgroup();
 		parent = NULL;
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+		WARN_ON(cgroup_add_cftypes(&mem_cgroup_subsys,
+					   kmem_cgroup_files));
+#endif
+
 		if (mem_cgroup_soft_limit_tree_init())
 			goto free_out;
 		root_mem_cgroup = memcg;
@@ -4997,6 +5072,7 @@ mem_cgroup_create(struct cgroup *cont)
 	if (parent && parent->use_hierarchy) {
 		res_counter_init(&memcg->res, &parent->res);
 		res_counter_init(&memcg->memsw, &parent->memsw);
+		res_counter_init(&memcg->kmem, &parent->kmem);
 		/*
 		 * We increment refcnt of the parent to ensure that we can
 		 * safely access it on res_counter_charge/uncharge.
@@ -5007,6 +5083,7 @@ mem_cgroup_create(struct cgroup *cont)
 	} else {
 		res_counter_init(&memcg->res, NULL);
 		res_counter_init(&memcg->memsw, NULL);
+		res_counter_init(&memcg->kmem, NULL);
 	}
 	memcg->last_scanned_node = MAX_NUMNODES;
 	INIT_LIST_HEAD(&memcg->oom_notify);
@@ -5014,6 +5091,7 @@ mem_cgroup_create(struct cgroup *cont)
 	if (parent)
 		memcg->swappiness = mem_cgroup_swappiness(parent);
 	atomic_set(&memcg->refcnt, 1);
+	memcg->kmem_accounted = false;
 	memcg->move_charge_at_immigrate = 0;
 	mutex_init(&memcg->thresholds_lock);
 	spin_lock_init(&memcg->move_lock);
-- 
1.7.7.6