mem_cgroup_events_index is a translation table to get the right index of
the memcg relevant entry for the general vm_event_item. At the moment,
it is defined as integer array. However on a typical system the max
entry of vm_event_item (NR_VM_EVENT_ITEMS) is 113, so we don't need to
use int as storage type of the array. For now just use int8_t as type
and add a BUILD_BUG_ON() and will switch to short once NR_VM_EVENT_ITEMS
touches 127.
Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
---
mm/memcontrol.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 602ad5faad4d..53769d06053f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -607,11 +607,14 @@ static const unsigned int memcg_vm_event_stat[] = {
};
#define NR_MEMCG_EVENTS ARRAY_SIZE(memcg_vm_event_stat)
-static int mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly;
+static int8_t mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly;
static void init_memcg_events(void)
{
- int i;
+ int8_t i;
+
+ /* Switch to short once this failure occurs. */
+ BUILD_BUG_ON(NR_VM_EVENT_ITEMS >= 127 /* INT8_MAX */);
for (i = 0; i < NR_MEMCG_EVENTS; ++i)
mem_cgroup_events_index[memcg_vm_event_stat[i]] = i + 1;
--
2.43.0
