mm, memcontrol: avoid duplicated memcg enable check

Patch series "mm/swap_cgroup: remove global swap cgroup lock", v3.

This series removes the global swap cgroup lock.  The critical section of
this lock is very short but it's still a bottle neck for mass parallel
swap workloads.

Up to 10% performance gain for tmpfs build kernel test on a 48c96t system
under memory pressure, and no regression for other cases:

This patch (of 3):

mem_cgroup_uncharge_swap() includes a mem_cgroup_disabled() check,
so the caller doesn't need to check that.

Link: https://lkml.kernel.org/r/20241218114633.85196-1-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20241218114633.85196-2-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Barry Song <baohua@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7ddbb2d12eb9218943a803eb455c510c5736128a..5c373d275e7a9748f91171ba00f4168b6042ab35 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4595,7 +4595,7 @@ void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
         * correspond 1:1 to page and swap slot lifetimes: we charge the
         * page to memory here, and uncharge swap when the slot is freed.
         */
-       if (!mem_cgroup_disabled() && do_memsw_account()) {
+       if (do_memsw_account()) {
                /*
                 * The swap entry might not get freed for a long time,
                 * let's not wait for it.  The page already received a