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 <[email protected]>
---
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
