On Mon 11-05-20 15:55:14, Jakub Kicinski wrote:
> Slice the memory overage calculation logic a little bit so we can
> reuse it to apply a similar penalty to the swap. The logic which
> accesses the memory-specific fields (use and high values) has to
> be taken out of calculate_high_delay().
>
> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
some recommendations below.
> ---
> mm/memcontrol.c | 62 ++++++++++++++++++++++++++++---------------------
> 1 file changed, 35 insertions(+), 27 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 05dcb72314b5..8a9b671c3249 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2321,41 +2321,48 @@ static void high_work_func(struct work_struct *work)
> #define MEMCG_DELAY_PRECISION_SHIFT 20
> #define MEMCG_DELAY_SCALING_SHIFT 14
>
> -/*
> - * Get the number of jiffies that we should penalise a mischievous cgroup which
> - * is exceeding its memory.high by checking both it and its ancestors.
> - */
> -static unsigned long calculate_high_delay(struct mem_cgroup *memcg,
> - unsigned int nr_pages)
> +static u64 calculate_overage(unsigned long usage, unsigned long high)
the naming is slightly confusing. I would concider the return value
to be in memory units rather than time because I would read it as
overrage of high. calculate_throttle_penalty would be more clear to me.
> {
> - unsigned long penalty_jiffies;
> - u64 max_overage = 0;
> -
> - do {
> - unsigned long usage, high;
> - u64 overage;
> + u64 overage;
>
> - usage = page_counter_read(&memcg->memory);
> - high = READ_ONCE(memcg->high);
> + if (usage <= high)
> + return 0;
>
> - if (usage <= high)
> - continue;
> + /*
> + * Prevent division by 0 in overage calculation by acting as if
> + * it was a threshold of 1 page
> + */
> + high = max(high, 1UL);
>
> - /*
> - * Prevent division by 0 in overage calculation by acting as if
> - * it was a threshold of 1 page
> - */
> - high = max(high, 1UL);
> + overage = usage - high;
> + overage <<= MEMCG_DELAY_PRECISION_SHIFT;
> + return div64_u64(overage, high);
> +}
>
> - overage = usage - high;
> - overage <<= MEMCG_DELAY_PRECISION_SHIFT;
> - overage = div64_u64(overage, high);
> +static u64 mem_find_max_overage(struct mem_cgroup *memcg)
This would then become find_high_throttle_penalty
> +{
> + u64 overage, max_overage = 0;
>
> - if (overage > max_overage)
> - max_overage = overage;
> + do {
> + overage = calculate_overage(page_counter_read(&memcg->memory),
> + READ_ONCE(memcg->high));
> + max_overage = max(overage, max_overage);
> } while ((memcg = parent_mem_cgroup(memcg)) &&
> !mem_cgroup_is_root(memcg));
>
> + return max_overage;
> +}
> +
> +/*
> + * Get the number of jiffies that we should penalise a mischievous cgroup which
> + * is exceeding its memory.high by checking both it and its ancestors.
> + */
> +static unsigned long calculate_high_delay(struct mem_cgroup *memcg,
> + unsigned int nr_pages,
> + u64 max_overage)
> +{
> + unsigned long penalty_jiffies;
> +
> if (!max_overage)
> return 0;
>
> @@ -2411,7 +2418,8 @@ void mem_cgroup_handle_over_high(void)
> * memory.high is breached and reclaim is unable to keep up. Throttle
> * allocators proactively to slow down excessive growth.
> */
> - penalty_jiffies = calculate_high_delay(memcg, nr_pages);
> + penalty_jiffies = calculate_high_delay(memcg, nr_pages,
> + mem_find_max_overage(memcg));
>
> /*
> * Don't sleep if the amount of jiffies this memcg owes us is so low
> --
> 2.25.4
--
Michal Hocko
SUSE Labs
