If the usage of a memcg is zero, we don't need to do useless work to scan
it. That is a minor optimization.
Cc: Roman Gushchin <guro@xxxxxx>
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
include/linux/memcontrol.h | 1 +
mm/memcontrol.c | 2 +-
mm/vmscan.c | 6 ++++++
3 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 612a457..1a315c7 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -54,6 +54,7 @@ enum mem_cgroup_protection {
MEMCG_PROT_NONE,
MEMCG_PROT_LOW,
MEMCG_PROT_MIN,
+ MEMCG_PROT_SKIP, /* For zero usage case */
};
struct mem_cgroup_reclaim_cookie {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c5b5f74..f35fcca 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6292,7 +6292,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
usage = page_counter_read(&memcg->memory);
if (!usage)
- return MEMCG_PROT_NONE;
+ return MEMCG_PROT_SKIP;
emin = memcg->memory.min;
elow = memcg->memory.low;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5a6445e..3c4c2da 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2677,6 +2677,12 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
* thresholds (see get_scan_count).
*/
break;
+ case MEMCG_PROT_SKIP:
+ /*
+ * Skip scanning this memcg if the usage of it is
+ * zero.
+ */
+ continue;
}
reclaimed = sc->nr_reclaimed;
--
1.8.3.1
