On 9/14/20 7:48 AM, Michal Hocko wrote:
On Sun 13-09-20 22:44:51, 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 | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8c74f1200261..ca36bed588d1 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1633,17 +1633,15 @@ 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)) + max = memcg->memsw.max;I agree that making v1 vs. v2 distinction here makes the code more obvious. But I do not think your code is correct for v1. In a default state it would lead to max = PAGE_COUNTER_MAX which is not something we want, right? instead you want max += min(READ_ONCE(memcg->memsw.max), total_swap_pages);
You are right, it is a bit tricky for v1. I will change it to max += min(READ_ONCE(memcg->memsw.max) - max, total_swap_pages): Thanks, Longman
