Basic kernel memory functionality for the Memory Controller

This patch lays down the foundation for the kernel memory component
of the Memory Controller.

As of today, I am only laying down the following files:

 * memory.independent_kmem_limit
 * memory.kmem.limit_in_bytes (currently ignored)
 * memory.kmem.usage_in_bytes (always zero)

Signed-off-by: Glauber Costa <glommer@parallels.com>
CC: Kirill A. Shutemov <kirill@shutemov.name>
CC: Paul Menage <paul@paulmenage.org>
CC: Greg Thelen <gthelen@google.com>
CC: Johannes Weiner <jweiner@redhat.com>
CC: Michal Hocko <mhocko@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 149 insertions, 7 deletions

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index cc0ebc5241b3..f2453241142b 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -44,8 +44,9 @@ Features:
  - oom-killer disable knob and oom-notifier
  - Root cgroup has no limit controls.
 
- Kernel memory and Hugepages are not under control yet. We just manage
- pages on LRU. To add more controls, we have to take care of performance.
+ Hugepages is not under control yet. We just manage pages on LRU. To add more
+ controls, we have to take care of performance. Kernel memory support is work
+ in progress, and the current version provides basically functionality.
 
 Brief summary of control files.
 
@@ -56,8 +57,11 @@ Brief summary of control files.
                                  (See 5.5 for details)
  memory.memsw.usage_in_bytes     # show current res_counter usage for memory+Swap
                                  (See 5.5 for details)
+ memory.kmem.usage_in_bytes      # show current res_counter usage for kmem only.
+                                 (See 2.7 for details)
  memory.limit_in_bytes           # set/show limit of memory usage
  memory.memsw.limit_in_bytes     # set/show limit of memory+Swap usage
+ memory.kmem.limit_in_bytes      # if allowed, set/show limit of kernel memory
  memory.failcnt                  # show the number of memory usage hits limits
  memory.memsw.failcnt            # show the number of memory+Swap hits limits
  memory.max_usage_in_bytes       # show max memory usage recorded
@@ -72,6 +76,9 @@ Brief summary of control files.
  memory.oom_control              # set/show oom controls.
  memory.numa_stat                # show the number of memory usage per numa node
 
+ memory.independent_kmem_limit   # select whether or not kernel memory limits are
+                                   independent of user limits
+
 1. History
 
 The memory controller has a long history. A request for comments for the memory
@@ -255,6 +262,35 @@ When oom event notifier is registered, event will be delivered.
   per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
   zone->lru_lock, it has no lock of its own.
 
+2.7 Kernel Memory Extension (CONFIG_CGROUP_MEM_RES_CTLR_KMEM)
+
+With the Kernel memory extension, the Memory Controller is able to limit
+the amount of kernel memory used by the system. Kernel memory is fundamentally
+different than user memory, since it can't be swapped out, which makes it
+possible to DoS the system by consuming too much of this precious resource.
+
+Some kernel memory resources may be accounted and limited separately from the
+main "kmem" resource. For instance, a slab cache that is considered important
+enough to be limited separately may have its own knobs.
+
+Kernel memory limits are not imposed for the root cgroup. Usage for the root
+cgroup may or may not be accounted.
+
+Memory limits as specified by the standard Memory Controller may or may not
+take kernel memory into consideration. This is achieved through the file
+memory.independent_kmem_limit. A Value different than 0 will allow for kernel
+memory to be controlled separately.
+
+When kernel memory limits are not independent, the limit values set in
+memory.kmem files are ignored.
+
+Currently no soft limit is implemented for kernel memory. It is future work
+to trigger slab reclaim when those limits are reached.
+
+2.7.1 Current Kernel Memory resources accounted
+
+None
+
 3. User Interface
 
 0. Configuration
diff --git a/init/Kconfig b/init/Kconfig
index 43298f9810fb..b8930d5a8325 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -689,6 +689,17 @@ config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
           For those who want to have the feature enabled by default should
           select this option (if, for some reason, they need to disable it
           then swapaccount=0 does the trick).
+config CGROUP_MEM_RES_CTLR_KMEM
+        bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
+        depends on CGROUP_MEM_RES_CTLR && EXPERIMENTAL
+        default n
+        help
+          The Kernel Memory extension for Memory Resource Controller can limit
+          the amount of memory used by kernel objects in the system. Those are
+          fundamentally different from the entities handled by the standard
+          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_PERF
         bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6aff93c98aca..9fbcff71245e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -227,6 +227,10 @@ struct mem_cgroup {
          */
         struct res_counter memsw;
         /*
+         * the counter to account for kmem usage.
+         */
+        struct res_counter kmem;
+        /*
          * Per cgroup active and inactive list, similar to the
          * per zone LRU lists.
          */
@@ -277,6 +281,11 @@ struct mem_cgroup {
          */
         unsigned long   move_charge_at_immigrate;
         /*
+         * Should kernel memory limits be stabilished independently
+         * from user memory ?
+         */
+        int             kmem_independent_accounting;
+        /*
          * percpu counter.
          */
         struct mem_cgroup_stat_cpu *stat;
@@ -344,9 +353,14 @@ enum charge_type {
 };
 
 /* for encoding cft->private value on file */
-#define _MEM                    (0)
-#define _MEMSWAP                (1)
-#define _OOM_TYPE               (2)
+
+enum mem_type {
+        _MEM = 0,
+        _MEMSWAP,
+        _OOM_TYPE,
+        _KMEM,
+};
+
 #define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
 #define MEMFILE_TYPE(val)       (((val) >> 16) & 0xffff)
 #define MEMFILE_ATTR(val)       ((val) & 0xffff)
@@ -3848,10 +3862,17 @@ static inline u64 mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
         u64 val;
 
         if (!mem_cgroup_is_root(memcg)) {
+                val = 0;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+                if (!memcg->kmem_independent_accounting)
+                        val = res_counter_read_u64(&memcg->kmem, RES_USAGE);
+#endif
                 if (!swap)
-                        return res_counter_read_u64(&memcg->res, RES_USAGE);
+                        val += res_counter_read_u64(&memcg->res, RES_USAGE);
                 else
-                        return res_counter_read_u64(&memcg->memsw, RES_USAGE);
+                        val += res_counter_read_u64(&memcg->memsw, RES_USAGE);
+
+                return val;
         }
 
         val = mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_CACHE);
@@ -3884,6 +3905,11 @@ static u64 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();
                 break;
@@ -4612,6 +4638,69 @@ static int mem_control_numa_stat_open(struct inode *unused, struct file *file)
 }
 #endif /* CONFIG_NUMA */
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+static u64 kmem_limit_independent_read(struct cgroup *cgroup, struct cftype *cft)
+{
+        return mem_cgroup_from_cont(cgroup)->kmem_independent_accounting;
+}
+
+static int kmem_limit_independent_write(struct cgroup *cgroup, struct cftype *cft,
+                                        u64 val)
+{
+        struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
+        struct mem_cgroup *parent = parent_mem_cgroup(memcg);
+
+        val = !!val;
+
+        /*
+         * This follows the same hierarchy restrictions than
+         * mem_cgroup_hierarchy_write()
+         */
+        if (!parent || !parent->use_hierarchy) {
+                if (list_empty(&cgroup->children))
+                        memcg->kmem_independent_accounting = val;
+                else
+                        return -EBUSY;
+        }
+        else
+                return -EINVAL;
+
+        return 0;
+}
+static struct cftype kmem_cgroup_files[] = {
+        {
+                .name = "independent_kmem_limit",
+                .read_u64 = kmem_limit_independent_read,
+                .write_u64 = kmem_limit_independent_write,
+        },
+        {
+                .name = "kmem.usage_in_bytes",
+                .private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
+                .read_u64 = mem_cgroup_read,
+        },
+        {
+                .name = "kmem.limit_in_bytes",
+                .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
+                .read_u64 = mem_cgroup_read,
+        },
+};
+
+static int register_kmem_files(struct cgroup *cont, struct cgroup_subsys *ss)
+{
+        int ret = 0;
+
+        ret = cgroup_add_files(cont, ss, kmem_cgroup_files,
+                               ARRAY_SIZE(kmem_cgroup_files));
+        return ret;
+};
+
+#else
+static int register_kmem_files(struct cgroup *cont, struct cgroup_subsys *ss)
+{
+        return 0;
+}
+#endif
+
 static struct cftype mem_cgroup_files[] = {
         {
                 .name = "usage_in_bytes",
@@ -4925,6 +5014,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, 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.
@@ -4935,6 +5025,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, 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_child = 0;
         memcg->last_scanned_node = MAX_NUMNODES;
@@ -4978,6 +5069,10 @@ static int mem_cgroup_populate(struct cgroup_subsys *ss,
 
         if (!ret)
                 ret = register_memsw_files(cont, ss);
+
+        if (!ret)
+                ret = register_kmem_files(cont, ss);
+
         return ret;
 }