On 9/14/20 10:47 AM, Michal Hocko wrote:
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);
Right, I thought it was possible to set memsw lower than mem. It was not allowed. So the extra check is unnecessary. Will fix that.
Cheers, Longman
