From: Yafang Shao <laoar.shao@xxxxxxxxx>
Subject: mm/memcontrol.c: keep local VM counters in sync with the hierarchical ones
After 815744d75152 ("mm: memcontrol: don't batch updates of local VM stats
and events"), the local VM counter are not in sync with the hierarchical
ones.
Below is one example in a leaf memcg on my server (with 8 CPUs):
inactive_file 3567570944
total_inactive_file 3568029696
We find that the deviation is very great because the 'val' in
__mod_memcg_state() is in pages while the effective value in
memcg_stat_show() is in bytes.
So the maximum of this deviation between local VM stats and total VM stats
can be (32 * number_of_cpu * PAGE_SIZE), that may be an unacceptably great
value.
We should keep the local VM stats in sync with the total stats. In order
to keep this behavior the same across counters, this patch updates
__mod_lruvec_state() and __count_memcg_events() as well.
Link: http://lkml.kernel.org/r/1562851979-10610-1-git-send-email-laoar.shao@xxxxxxxxx
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Yafang Shao <shaoyafang@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
--- a/mm/memcontrol.c~mm-memcontrol-keep-local-vm-counters-in-sync-with-the-hierarchical-ones
+++ a/mm/memcontrol.c
@@ -695,12 +695,15 @@ void __mod_memcg_state(struct mem_cgroup
if (mem_cgroup_disabled())
return;
- __this_cpu_add(memcg->vmstats_local->stat[idx], val);
-
x = val + __this_cpu_read(memcg->vmstats_percpu->stat[idx]);
if (unlikely(abs(x) > MEMCG_CHARGE_BATCH)) {
struct mem_cgroup *mi;
+ /*
+ * Batch local counters to keep them in sync with
+ * the hierarchical ones.
+ */
+ __this_cpu_add(memcg->vmstats_local->stat[idx], x);
for (mi = memcg; mi; mi = parent_mem_cgroup(mi))
atomic_long_add(x, &mi->vmstats[idx]);
x = 0;
@@ -749,13 +752,15 @@ void __mod_lruvec_state(struct lruvec *l
/* Update memcg */
__mod_memcg_state(memcg, idx, val);
- /* Update lruvec */
- __this_cpu_add(pn->lruvec_stat_local->count[idx], val);
-
x = val + __this_cpu_read(pn->lruvec_stat_cpu->count[idx]);
if (unlikely(abs(x) > MEMCG_CHARGE_BATCH)) {
struct mem_cgroup_per_node *pi;
+ /*
+ * Batch local counters to keep them in sync with
+ * the hierarchical ones.
+ */
+ __this_cpu_add(pn->lruvec_stat_local->count[idx], x);
for (pi = pn; pi; pi = parent_nodeinfo(pi, pgdat->node_id))
atomic_long_add(x, &pi->lruvec_stat[idx]);
x = 0;
@@ -777,12 +782,15 @@ void __count_memcg_events(struct mem_cgr
if (mem_cgroup_disabled())
return;
- __this_cpu_add(memcg->vmstats_local->events[idx], count);
-
x = count + __this_cpu_read(memcg->vmstats_percpu->events[idx]);
if (unlikely(x > MEMCG_CHARGE_BATCH)) {
struct mem_cgroup *mi;
+ /*
+ * Batch local counters to keep them in sync with
+ * the hierarchical ones.
+ */
+ __this_cpu_add(memcg->vmstats_local->events[idx], x);
for (mi = memcg; mi; mi = parent_mem_cgroup(mi))
atomic_long_add(x, &mi->vmevents[idx]);
x = 0;
_
