+ mm-memcg-simplify-mem_cgroup_get_max.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm/memcg: simplify mem_cgroup_get_max()
has been added to the -mm tree.  Its filename is
     mm-memcg-simplify-mem_cgroup_get_max.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-simplify-mem_cgroup_get_max.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-simplify-mem_cgroup_get_max.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Waiman Long <longman@redhat.com>
Subject: mm/memcg: simplify mem_cgroup_get_max()

mem_cgroup_get_max() 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.

Link: https://lkml.kernel.org/r/20200914024452.19167-3-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |   18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

--- a/mm/memcontrol.c~mm-memcg-simplify-mem_cgroup_get_max
+++ a/mm/memcontrol.c
@@ -1635,17 +1635,15 @@ void mem_cgroup_print_oom_meminfo(struct
  */
 unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg)
 {
-	unsigned long max;
+	unsigned long max = READ_ONCE(memcg->memory.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);
+	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;
 	}
 	return max;
 }
_

Patches currently in -mm which might be from longman@redhat.com are

mm-memcg-clean-up-obsolete-enum-charge_type.patch
mm-memcg-simplify-mem_cgroup_get_max.patch
mm-memcg-unify-swap-and-memsw-page-counters.patch