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Date:   Mon, 7 Dec 2020 12:01:55 -0800
From:   Roman Gushchin <guro@fb.com>
To:     Muchun Song <songmuchun@bytedance.com>
CC:     <gregkh@linuxfoundation.org>, <rafael@kernel.org>,
        <adobriyan@gmail.com>, <akpm@linux-foundation.org>,
        <hannes@cmpxchg.org>, <mhocko@kernel.org>,
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Subject: Re: [RESEND PATCH v2 09/12] mm: memcontrol: convert vmstat slab
 counters to bytes
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On Mon, Dec 07, 2020 at 11:46:22AM -0800, Roman Gushchin wrote:
> On Sun, Dec 06, 2020 at 06:14:48PM +0800, Muchun Song wrote:
> > the global and per-node counters are stored in pages, however memcg
> > and lruvec counters are stored in bytes. This scheme looks weird.
> > So convert all vmstat slab counters to bytes.
> 
> There is a reason for this weird scheme:
> percpu caches (see struct per_cpu_nodestat) are s8, so counting in bytes
> will lead to overfills. Switching to s32 can lead to an increase in
> the cache thrashing, especially on small machines.

JFYI:
I've tried to convert all slab counters to bytes and change those s8 percpu batches to s32
about a year ago. Here is a link to that thread:
https://patchwork.kernel.org/project/linux-mm/patch/20191018002820.307763-3-guro@fb.com/

Thanks!