mem_cgroup_force_empty_list() can iterate a large number of pages on an lru and
mem_cgroup_move_parent() doesn't return an errno unless certain criteria, none
of which indicate that the iteration may be taking too long, is met.
We have encountered the following stack trace many times indicating
"need_resched set for > 51000020 ns (51 ticks) without schedule", for example:
scheduler_tick()
<timer irq>
mem_cgroup_move_account+0x4d/0x1d5
mem_cgroup_move_parent+0x8d/0x109
mem_cgroup_reparent_charges+0x149/0x2ba
mem_cgroup_css_offline+0xeb/0x11b
cgroup_offline_fn+0x68/0x16b
process_one_work+0x129/0x350
If this iteration is taking too long, indicated by need_resched(), then
periodically schedule and continue from where we last left off.
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
mm/memcontrol.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4764,6 +4764,7 @@ static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
do {
struct page_cgroup *pc;
struct page *page;
+ int ret;
spin_lock_irqsave(&zone->lru_lock, flags);
if (list_empty(list)) {
@@ -4781,8 +4782,13 @@ static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
pc = lookup_page_cgroup(page);
- if (mem_cgroup_move_parent(page, pc, memcg)) {
- /* found lock contention or "pc" is obsolete. */
+ ret = mem_cgroup_move_parent(page, pc, memcg);
+ if (ret || need_resched()) {
+ /*
+ * Couldn't grab the page reference, isolate the page,
+ * there was a pc mismatch, or we simply need to
+ * schedule because this is taking too long.
+ */
busy = page;
cond_resched();
} else
--
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