[Devel] [PATCH 08/10] memcg: Add CONFIG_CGROUP_MEM_RES_CTLR_KMEM_ACCT_ROOT.

[Suleiman Souhlal]

This config option dictates whether or not kernel memory in the
root cgroup should be accounted.

This may be useful in an environment where everything is supposed to be
in a cgroup and accounted for. Large amounts of kernel memory in the
root cgroup would indicate problems with memory isolation or accounting.

Signed-off-by: Suleiman Souhlal <suleiman at google.com>
---
 init/Kconfig    |    8 ++++++++
 mm/memcontrol.c |   44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 0 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 3f42cd6..a119270 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -714,6 +714,14 @@ config CGROUP_MEM_RES_CTLR_KMEM
 	  Memory Controller, which are page-based, and can be swapped. Users of
 	  the kmem extension can use it to guarantee that no group of processes
 	  will ever exhaust kernel resources alone.
+config CGROUP_MEM_RES_CTLR_KMEM_ACCT_ROOT
+	bool "Root Cgroup Kernel Memory Accounting (EXPERIMENTAL)"
+	depends on CGROUP_MEM_RES_CTLR_KMEM
+	default n
+	help
+	  Account for kernel memory used by the root cgroup. This may be useful
+	  to know how much kernel memory isn't currently accounted to any
+	  cgroup.
 
 config CGROUP_PERF
 	bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6a475ed..d4cdb8e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -61,6 +61,10 @@ struct cgroup_subsys mem_cgroup_subsys __read_mostly;
 #define MEM_CGROUP_RECLAIM_RETRIES	5
 struct mem_cgroup *root_mem_cgroup __read_mostly;
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM_ACCT_ROOT
+atomic64_t pre_memcg_kmem_bytes;	/* kmem usage before memcg is enabled */
+#endif
+
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 /* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
 int do_swap_account __read_mostly;
@@ -5643,6 +5647,13 @@ memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, long long delta)
 
 	if (memcg)
 		ret = res_counter_charge(&memcg->kmem_bytes, delta, &fail_res);
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM_ACCT_ROOT
+	else if (root_mem_cgroup != NULL)
+		ret = res_counter_charge(&root_mem_cgroup->kmem_bytes, delta,
+		    &fail_res);
+	else
+		atomic64_add(delta, &pre_memcg_kmem_bytes);
+#endif
 
 	return ret;
 }
@@ -5668,6 +5679,12 @@ memcg_uncharge_kmem(struct mem_cgroup *memcg, long long delta)
 
 	if (memcg)
 		res_counter_uncharge(&memcg->kmem_bytes, delta);
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM_ACCT_ROOT
+	else if (root_mem_cgroup != NULL)
+		res_counter_uncharge(&root_mem_cgroup->kmem_bytes, delta);
+	else
+		atomic64_sub(delta, &pre_memcg_kmem_bytes);
+#endif
 
 	if (memcg && !memcg->independent_kmem_limit)
 		res_counter_uncharge(&memcg->res, delta);
@@ -5953,7 +5970,12 @@ memcg_slab_move(struct mem_cgroup *memcg)
 		cachep = rcu_access_pointer(memcg->slabs[i]);
 		if (cachep != NULL) {
 			rcu_assign_pointer(memcg->slabs[i], NULL);
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM_ACCT_ROOT
+			cachep->memcg = root_mem_cgroup;
+#else
 			cachep->memcg = NULL;
+#endif
 
 			/* The space for this is already allocated */
 			strcat((char *)cachep->name, "dead");
@@ -5991,6 +6013,15 @@ memcg_kmem_init(struct mem_cgroup *memcg, struct mem_cgroup *parent)
 
 	memcg_slab_init(memcg);
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM_ACCT_ROOT
+	if (memcg == root_mem_cgroup) {
+		long kmem_bytes;
+
+		kmem_bytes = atomic64_xchg(&pre_memcg_kmem_bytes, 0);
+		memcg->kmem_bytes.usage = kmem_bytes;
+	}
+#endif
+
 	atomic64_set(&memcg->kmem_bypassed, 0);
 	memcg->independent_kmem_limit = 0;
 }
@@ -6010,6 +6041,19 @@ memcg_kmem_move(struct mem_cgroup *memcg)
 	spin_unlock_irqrestore(&memcg->kmem_bytes.lock, flags);
 	if (!memcg->independent_kmem_limit)
 		res_counter_uncharge(&memcg->res, kmem_bytes);
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM_ACCT_ROOT
+	{
+		struct res_counter *dummy;
+		int err;
+
+		/* Can't fail because it's the root cgroup */
+		err = res_counter_charge(&root_mem_cgroup->kmem_bytes,
+		    kmem_bytes, &dummy);
+		err = res_counter_charge(&root_mem_cgroup->res, kmem_bytes,
+		    &dummy);
+	}
+#endif
 }
 #else /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
 static void
-- 
1.7.7.3