linux-kernel - Re: [PATCH v2] mm: memcg/slab: Fix root memcg vmstats

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Date:   Tue, 10 Nov 2020 10:57:23 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Muchun Song <songmuchun@...edance.com>
cc:     hannes@...xchg.org, mhocko@...nel.org, vdavydov.dev@...il.com,
        Andrew Morton <akpm@...ux-foundation.org>, cl@...ux.com,
        penberg@...nel.org, iamjoonsoo.kim@....com, shakeelb@...gle.com,
        guro@...com, Vlastimil Babka <vbabka@...e.cz>,
        laoar.shao@...il.com, chris@...isdown.name,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v2] mm: memcg/slab: Fix root memcg vmstats

On Tue, 10 Nov 2020, Muchun Song wrote:

> If we reparent the slab objects to the root memcg, when we free
> the slab object, we need to update the per-memcg vmstats to keep
> it correct for the root memcg. Now this at least affects the vmstat
> of NR_KERNEL_STACK_KB for !CONFIG_VMAP_STACK when the thread stack
> size is smaller than the PAGE_SIZE.
> 
> Fixes: ec9f02384f60 ("mm: workingset: fix vmstat counters for shadow nodes")
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> Acked-by: Roman Gushchin <guro@...com>

Acked-by: David Rientjes <rientjes@...gle.com>

I assume that without this fix that the root memcg's vmstat would always 
be inflated if we reparented?  If that's accurate, perhaps this is 
deserving of a

Cc: stable@...r.kernel.org # 5.3+