memcg: fix memory.high target
When the memory.high threshold is exceeded, try_charge() schedules a
task_work to reclaim the excess. The reclaim target is set to the
number of pages requested by try_charge().
This is wrong, because try_charge() usually charges more pages than
requested (batch > nr_pages) in order to refill per cpu stocks. As a
result, a process in a cgroup can easily exceed memory.high
significantly when doing a lot of charges w/o returning to userspace
(e.g. reading a file in big chunks).
Fix this issue by assuring that when exceeding memory.high a process
reclaims as many pages as were actually charged (i.e. batch).
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c92a65b..32259e3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2128,7 +2128,7 @@
*/
do {
if (page_counter_read(&memcg->memory) > memcg->high) {
- current->memcg_nr_pages_over_high += nr_pages;
+ current->memcg_nr_pages_over_high += batch;
set_notify_resume(current);
break;
}