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Date:   Wed, 10 Jun 2020 18:42:22 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Alex Shi <alex.shi@linux.alibaba.com>,
        Joonsoo Kim <js1304@gmail.com>,
        Shakeel Butt <shakeelb@google.com>,
        Hugh Dickins <hughd@google.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Roman Gushchin <guro@fb.com>, linux-mm@kvack.org,
        cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@fb.com
Subject: Re: [PATCH 09/19] mm: memcontrol: switch to native NR_FILE_PAGES and
 NR_SHMEM counters
Message-ID: <20200610164222.GE20204@dhcp22.suse.cz>
References: <20200508183105.225460-1-hannes@cmpxchg.org>
 <20200508183105.225460-10-hannes@cmpxchg.org>
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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@cmpxchg.org>
> Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

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