Re: mmotm 2019-07-24-21-39 uploaded (mm/memcontrol)

Andrew Morton
2019-07-27T04:19:58Z

On Fri, 26 Jul 2019 20:42:05 -0700 Nathan Chancellor <natechancellor@gmail.com> wrote:

> > @@ -2414,8 +2414,9 @@ void mem_cgroup_handle_over_high(void)
> > */
> > clamped_high = max(high, 1UL);
> >
> > - overage = ((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT)
> > - / clamped_high;
> > + overage = (u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT;
> > + do_div(overage, clamped_high);
> > +
> > penalty_jiffies = ((u64)overage * overage * HZ)
> > >> (MEMCG_DELAY_PRECISION_SHIFT + MEMCG_DELAY_SCALING_SHIFT);
> >
> > _
> >
>
> This causes a build error on arm:
>

Ah.

It's rather unclear why that u64 cast is there anyway. We're dealing
with ulongs all over this code. The below will suffice.

Chris, please take a look?

--- a/mm/memcontrol.c~mm-throttle-allocators-when-failing-reclaim-over-memoryhigh-fix-fix-fix
+++ a/mm/memcontrol.c
@@ -2415,7 +2415,7 @@ void mem_cgroup_handle_over_high(void)
clamped_high = max(high, 1UL);

overage = (u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT;
- do_div(overage, clamped_high);
+ overage /= clamped_high;

penalty_jiffies = ((u64)overage * overage * HZ)
>> (MEMCG_DELAY_PRECISION_SHIFT + MEMCG_DELAY_SCALING_SHIFT);
_