On 4/11/25 1:11 PM, Michal Koutný wrote:
Hello.
On Mon, Apr 07, 2025 at 12:23:15PM -0400, Waiman Long <[email protected]>
wrote:
--- a/mm/memcontrol-v1.h
+++ b/mm/memcontrol-v1.h
@@ -22,8 +22,6 @@
iter != NULL; \
iter = mem_cgroup_iter(NULL, iter, NULL))
-unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap);
-
Hm, maybe keep it for v1 only where mem_cgroup_usage has meaning for
memsw (i.e. do the opposite and move the function definition to -v1.c).
memcontrol-v1.c also include mm/internal.h. That is the reason why I can
remove it from here.
void drain_all_stock(struct mem_cgroup *root_memcg);
unsigned long memcg_events(struct mem_cgroup *memcg, int event);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b620d74b0f66..a771a0145a12 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -5963,6 +5963,10 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct
scan_control *sc)
mem_cgroup_calculate_protection(target_memcg, memcg);
+ /* Skip memcg with no usage */
+ if (!mem_cgroup_usage(memcg, false))
+ continue;
+
(Not only for v2), there is mem_cgroup_size() for this purpose (already
used in mm/vmscan.c).
My understanding is that mem_cgroup_usage() is for both v1 and v2, while
mem_cgroup_size() is for v2 only.
if (mem_cgroup_below_min(target_memcg, memcg)) {
/*
* Hard protection.
diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c
b/tools/testing/selftests/cgroup/test_memcontrol.c
index 16f5d74ae762..bab826b6b7b0 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -525,8 +525,13 @@ static int test_memcg_protection(const char *root, bool
min)
goto cleanup;
}
+ /*
+ * Child 2 has memory.low=0, but some low protection is still being
+ * distributed down from its parent with memory.low=50M. So the low
+ * event count will be non-zero.
+ */
for (i = 0; i < ARRAY_SIZE(children); i++) {
- int no_low_events_index = 1;
+ int no_low_events_index = 2;
See suggestion in
https://lore.kernel.org/lkml/awgbdn6gwnj4kfaezsorvopgsdyoty3yahdeanqvoxstz2w2ke@xc3sv43elkz5/
I have just replied on your suggestion.
Cheers,
Longman
HTH,
Michal
