If a memcg is over high limit, memory reclaim is scheduled to run on
return-to-userland. However it is assumed that the memcg is the current
process's memcg. With remote memcg charging for kmem or swapping in a
page charged to remote memcg, current process can trigger reclaim on
remote memcg. So, schduling reclaim on return-to-userland for remote
memcgs will ignore the high reclaim altogether. So, punt the high
reclaim of remote memcgs to high_work.
Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
---
mm/memcontrol.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e9db1160ccbc..47439c84667a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2302,19 +2302,23 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
* reclaim on returning to userland. We can perform reclaim here
* if __GFP_RECLAIM but let's always punt for simplicity and so that
* GFP_KERNEL can consistently be used during reclaim. @memcg is
- * not recorded as it most likely matches current's and won't
- * change in the meantime. As high limit is checked again before
- * reclaim, the cost of mismatch is negligible.
+ * not recorded as the return-to-userland high reclaim will only reclaim
+ * from current's memcg (or its ancestor). For other memcgs we punt them
+ * to work queue.
*/
do {
if (page_counter_read(&memcg->memory) > memcg->high) {
- /* Don't bother a random interrupted task */
- if (in_interrupt()) {
+ /*
+ * Don't bother a random interrupted task or if the
+ * memcg is not current's memcg's ancestor.
+ */
+ if (in_interrupt() ||
+ !mm_match_cgroup(current->mm, memcg)) {
schedule_work(&memcg->high_work);
- break;
+ } else {
+ current->memcg_nr_pages_over_high += batch;
+ set_notify_resume(current);
}
- current->memcg_nr_pages_over_high += batch;
- set_notify_resume(current);
break;
}
} while ((memcg = parent_mem_cgroup(memcg)));
--
2.20.1.415.g653613c723-goog
