[mm] [PATCH 4/4] Memory cgroup hierarchy feature selector

Balbir Singh
2008-11-01T18:49:41Z

Don't enable multiple hierarchy support by default. This patch introduces
a features element that can be set to enable the nested depth hierarchy
feature. This feature can only be enabled when there is just one cgroup
(the root cgroup).

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---

mm/memcontrol.c | 38 +++++++++++++++++++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)

diff -puN mm/memcontrol.c~memcg-add-hierarchy-selector mm/memcontrol.c
--- linux-2.6.28-rc2/mm/memcontrol.c~memcg-add-hierarchy-selector 2008-11-02 00:15:00.000000000 +0530
+++ linux-2.6.28-rc2-balbir/mm/memcontrol.c 2008-11-02 00:15:00.000000000 +0530
@@ -40,6 +40,9 @@
struct cgroup_subsys mem_cgroup_subsys __read_mostly;
#define MEM_CGROUP_RECLAIM_RETRIES 5

+static unsigned long mem_cgroup_features;
+#define MEM_CGROUP_FEAT_HIERARCHY 0x1
+
/*
* Statistics for memory cgroup.
*/
@@ -1080,6 +1083,31 @@ out:
return ret;
}

+static u64 mem_cgroup_feature_read(struct cgroup *cont, struct cftype *cft)
+{
+ return mem_cgroup_features;
+}
+
+static int mem_cgroup_feature_write(struct cgroup *cont, struct cftype *cft,
+ u64 val)
+{
+ int retval = 0;
+ struct cgroup *cgroup = init_mem_cgroup.css.cgroup;
+
+ if (val & MEM_CGROUP_FEAT_HIERARCHY) {
+ if (list_empty(&cgroup->children))
+ mem_cgroup_features |= MEM_CGROUP_FEAT_HIERARCHY;
+ else
+ retval = -EBUSY;
+ } else {
+ if (list_empty(&cgroup->children))
+ mem_cgroup_features &= ~MEM_CGROUP_FEAT_HIERARCHY;
+ else
+ retval = -EBUSY;
+ }
+ return retval;
+}
+
static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
{
return res_counter_read_u64(&mem_cgroup_from_cont(cont)->res,
@@ -1214,6 +1242,11 @@ static struct cftype mem_cgroup_files[]
.name = "stat",
.read_map = mem_control_stat_show,
},
+ {
+ .name = "features",
+ .write_u64 = mem_cgroup_feature_write,
+ .read_u64 = mem_cgroup_feature_read,
+ },
};

static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
@@ -1292,7 +1325,10 @@ mem_cgroup_create(struct cgroup_subsys *
return ERR_PTR(-ENOMEM);
}

- res_counter_init(&mem->res, parent ? &parent->res : NULL);
+ if ((mem_cgroup_features & MEM_CGROUP_FEAT_HIERARCHY) && parent)
+ res_counter_init(&mem->res, &parent->res);
+ else
+ res_counter_init(&mem->res, NULL);

for_each_node_state(node, N_POSSIBLE)
if (alloc_mem_cgroup_per_zone_info(mem, node))
_

--
Balbir