cgroup: Add kernel param to enable memory group

cgroup support is useful, but enabling the "memory" cgroup has a 32-byte
overhead per page. Arrange that "memory" cgroup is disabled by default
unless the "cgroup_memory" parameter is set to a true value.

See: https://github.com/raspberrypi/issues/1950

Signed-off-by: Phil Elwell <phil@raspberrypi.org>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2c785f9570243879d79b277d27393485824b5056..c3f5abf0fd7a47af325f97fa5342e799745fbeae 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5638,6 +5638,8 @@ int __init cgroup_init_early(void)
 }
 
 static u16 cgroup_disable_mask __initdata;
+static bool cgroup_enable_memory;
+static int __init cgroup_disable(char *str);
 
 /**
  * cgroup_init - cgroup initialization
@@ -5676,6 +5678,9 @@ int __init cgroup_init(void)
 
        mutex_unlock(&cgroup_mutex);
 
+       if (!cgroup_enable_memory)
+               cgroup_disable("memory");
+
        for_each_subsys(ss, ssid) {
                if (ss->early_init) {
                        struct cgroup_subsys_state *css =
@@ -6151,6 +6156,13 @@ static int __init cgroup_disable(char *str)
 }
 __setup("cgroup_disable=", cgroup_disable);
 
+static int __init cgroup_memory(char *str)
+{
+       kstrtobool(str, &cgroup_enable_memory);
+       return 1;
+}
+__setup("cgroup_memory=", cgroup_memory);
+
 static int __init cgroup_no_v1(char *str)
 {
        struct cgroup_subsys *ss;