linux-kernel - Re: [PATCH v2] mm: shmem: Rename mTHP shmem counters

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Message-ID: <efa45499-0080-4bb1-85b3-e88ed19688dd@redhat.com>
Date: Wed, 10 Jul 2024 20:30:12 +0200
From: David Hildenbrand <david@...hat.com>
To: Ryan Roberts <ryan.roberts@....com>,
 Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins <hughd@...gle.com>,
 Jonathan Corbet <corbet@....net>, Barry Song <baohua@...nel.org>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>, Lance Yang
 <ioworker0@...il.com>, Matthew Wilcox <willy@...radead.org>,
 Zi Yan <ziy@...dia.com>, Daniel Gomez <da.gomez@...sung.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2] mm: shmem: Rename mTHP shmem counters

On 10.07.24 11:55, Ryan Roberts wrote:
> The legacy PMD-sized THP counters at /proc/vmstat include
> thp_file_alloc, thp_file_fallback and thp_file_fallback_charge, which
> rather confusingly refer to shmem THP and do not include any other types
> of file pages. This is inconsistent since in most other places in the
> kernel, THP counters are explicitly separated for anon, shmem and file
> flavours. However, we are stuck with it since it constitutes a user ABI.
> 
> Recently, commit 66f44583f9b6 ("mm: shmem: add mTHP counters for
> anonymous shmem") added equivalent mTHP stats for shmem, keeping the
> same "file_" prefix in the names. But in future, we may want to add
> extra stats to cover actual file pages, at which point, it would all
> become very confusing.
> 
> So let's take the opportunity to rename these new counters "shmem_"
> before the change makes it upstream and the ABI becomes immutable. While
> we are at it, let's improve the documentation for the legacy counters to
> make it clear that they count shmem pages only.
> 
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Reviewed-by: Lance Yang <ioworker0@...il.com>
> ---

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb