Re: [PATCH 09/19] mm: memcontrol: switch to native NR_FILE_PAGES and NR_SHMEM counters

[Michal Hocko]

On Fri 08-05-20 14:30:56, Johannes Weiner wrote:
> Memcg maintains private MEMCG_CACHE and NR_SHMEM counters. This
> divergence from the generic VM accounting means unnecessary code
> overhead, and creates a dependency for memcg that page->mapping is set
> up at the time of charging, so that page types can be told apart.
> 
> Convert the generic accounting sites to mod_lruvec_page_state and
> friends to maintain the per-cgroup vmstat counters of NR_FILE_PAGES
> and NR_SHMEM. The page is already locked in these places, so
> page->mem_cgroup is stable; we only need minimal tweaks of two
> mem_cgroup_migrate() calls to ensure it's set up in time.
> 
> Then replace MEMCG_CACHE with NR_FILE_PAGES and delete the private
> NR_SHMEM accounting sites.
> 
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

While looking at the code I've noticed that add_to_swap_cache resp.
__delete_from_swap_cache are accounting only to global counters.
Is there any reason for that? Not something that this patch is
responsible for of course but I am just wondering.
-- 
Michal Hocko
SUSE Labs