For fast cpus on slow disks, yielding the cpus repeatedly with
PR_MEMACT_SLOWDOWN may not be able to slow down memory allocation enough
for memory reclaim to catch up. In case a large memory block is mmap'ed
and the pages are faulted in one-by-one, the syscall delays won't be
activated during this process.
To be safe, an additional variable delay of 20-5000 us will be added
to __mem_cgroup_over_high_action() if the excess memory used is more
than 1/256 of the memory limit.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
mm/memcontrol.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6488f8a10d66..bddf3e659469 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2643,11 +2643,10 @@ get_rss_counter(struct mm_struct *mm, int mm_bit, u16 flags, int rss_bit)
static bool __mem_cgroup_over_high_action(struct mem_cgroup *memcg, u8 action,
u16 flags)
{
- unsigned long mem = 0;
+ unsigned long mem = 0, limit = 0, excess = 0;
bool ret = false;
struct mm_struct *mm = get_task_mm(current);
u8 signal = READ_ONCE(current->memcg_over_high_signal);
- u32 limit;
if (!mm)
return true; /* No more check is needed */
@@ -2657,9 +2656,10 @@ static bool __mem_cgroup_over_high_action(struct mem_cgroup *memcg, u8 action,
if (memcg) {
mem = page_counter_read(&memcg->memory);
- limit = READ_ONCE(current->memcg_over_high_climit);
- if (mem <= memcg->memory.high + limit)
+ limit = READ_ONCE(current->memcg_over_high_climit) + memcg->memory.high;
+ if (mem <= limit)
goto out;
+ excess = mem - limit;
}
/*
@@ -2676,6 +2676,7 @@ static bool __mem_cgroup_over_high_action(struct mem_cgroup *memcg, u8 action,
limit = READ_ONCE(current->memcg_over_high_plimit);
if (mem <= limit)
goto out;
+ excess = mem - limit;
}
ret = true;
@@ -2685,10 +2686,19 @@ static bool __mem_cgroup_over_high_action(struct mem_cgroup *memcg, u8 action,
break;
case PR_MEMACT_SLOWDOWN:
/*
- * Slow down by yielding the cpu & adding delay to
- * memory allocation syscalls.
+ * Slow down by yielding the cpu & adding delay to memory
+ * allocation syscalls.
+ *
+ * An additional 20-5000 us of delay is added in case the
+ * excess memory is more than 1/256 of the limit.
*/
WRITE_ONCE(current->memcg_over_limit, true);
+ limit >>= 8;
+ if (limit && (excess > limit)) {
+ int delay = min(5000UL, excess/limit * 20UL);
+
+ udelay(delay);
+ }
set_tsk_need_resched(current);
set_preempt_need_resched();
break;
--
2.18.1
