On Mon 14-09-20 10:19:55, Waiman Long wrote:
> The mem_cgroup_get_max() function used to get memory+swap max from
> both the v1 memsw and v2 memory+swap page counters & return the maximum
> of these 2 values. This is redundant and it is more efficient to just
> get either the v1 or the v2 values depending on which one is currently
> in use.
>
> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> ---
> mm/memcontrol.c | 24 +++++++++++++-----------
> 1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 8c74f1200261..2331d4bc7c4d 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1633,17 +1633,19 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
> */
> unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg)
> {
> - unsigned long max;
> -
> - max = READ_ONCE(memcg->memory.max);
> - if (mem_cgroup_swappiness(memcg)) {
> - unsigned long memsw_max;
> - unsigned long swap_max;
> -
> - memsw_max = memcg->memsw.max;
> - swap_max = READ_ONCE(memcg->swap.max);
> - swap_max = min(swap_max, (unsigned long)total_swap_pages);
> - max = min(max + swap_max, memsw_max);
> + unsigned long max = READ_ONCE(memcg->memory.max);
> +
> + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
> + if (mem_cgroup_swappiness(memcg))
> + max += min(READ_ONCE(memcg->swap.max),
> + (unsigned long)total_swap_pages);
> + } else { /* v1 */
> + if (mem_cgroup_swappiness(memcg)) {
> + unsigned long memsw = READ_ONCE(memcg->memsw.max);
> +
> + if (memsw > max)
> + max += min(memsw - max, (unsigned long)total_swap_pages);
Yes this looks better. But, memsw can never be smaller than the hard
limit (mem_cgroup_resize_max). I would find it slightly easier to
understand if you did
/* calculate swap excess capacity from memsw limit*/
unsigned long memsw = READ_ONCE(memcg->memsw.max) - max;
max += min (memsw, total_swap_pages);
> + }
> }
> return max;
> }
> --
> 2.18.1
--
Michal Hocko
SUSE Labs
