[patch 04/11] mm, memcg: add tunable for oom reserves

David Rientjes
2014-03-05T03:59:19Z

Userspace needs a way to define the amount of memory reserves that
processes handling oom conditions may utilize. This patch adds a per-
memcg oom reserve field and file, memory.oom_reserve_in_bytes, to
manipulate its value.

If currently utilized memory reserves are attempted to be reduced by
writing a smaller value to memory.oom_reserve_in_bytes, it will fail with
-EBUSY until some memory is uncharged.

Signed-off-by: David Rientjes <rientjes@google.com>
---
mm/memcontrol.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -315,6 +315,9 @@ struct mem_cgroup {
/* OOM-Killer disable */
int oom_kill_disable;

+ /* reserves for handling oom conditions, protected by res.lock */
+ unsigned long long oom_reserve;
+
/* set when res.limit == memsw.limit */
bool memsw_is_minimum;

@@ -5936,6 +5939,51 @@ static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
return 0;
}

+static int mem_cgroup_resize_oom_reserve(struct mem_cgroup *memcg,
+ unsigned long long new_limit)
+{
+ struct res_counter *res = &memcg->res;
+ u64 limit, usage;
+ int ret = 0;
+
+ spin_lock(&res->lock);
+ limit = res->limit;
+ usage = res->usage;
+
+ if (usage > limit && usage - limit > new_limit) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ memcg->oom_reserve = new_limit;
+out:
+ spin_unlock(&res->lock);
+ return ret;
+}
+
+static u64 mem_cgroup_oom_reserve_read(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return mem_cgroup_from_css(css)->oom_reserve;
+}
+
+static int mem_cgroup_oom_reserve_write(struct cgroup_subsys_state *css,
+ struct cftype *cft, const char *buffer)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_css(css);
+ unsigned long long val;
+ int ret;
+
+ if (mem_cgroup_is_root(memcg))
+ return -EINVAL;
+
+ ret = res_counter_memparse_write_strategy(buffer, &val);
+ if (ret)
+ return ret;
+
+ return mem_cgroup_resize_oom_reserve(memcg, val);
+}
+
#ifdef CONFIG_MEMCG_KMEM
static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
{
@@ -6291,6 +6339,11 @@ static struct cftype mem_cgroup_files[] = {
.private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
},
{
+ .name = "oom_reserve_in_bytes",
+ .read_u64 = mem_cgroup_oom_reserve_read,
+ .write_string = mem_cgroup_oom_reserve_write,
+ },
+ {
.name = "pressure_level",
},
#ifdef CONFIG_NUMA