linux-kernel - Re: [PATCH v4 01/15] docs/mm: add document for swap table

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Message-ID: <CAGsJ_4zmkibM_Ex7kGMsr2sni85H-cnxQvh0XwkWiALNQy+zAQ@mail.gmail.com>
Date: Thu, 18 Sep 2025 16:58:52 +0800
From: Barry Song <21cnbao@...il.com>
To: Chris Li <chrisl@...nel.org>
Cc: Kairui Song <ryncsn@...il.com>, linux-mm@...ck.org, 
	Andrew Morton <akpm@...ux-foundation.org>, Matthew Wilcox <willy@...radead.org>, 
	Hugh Dickins <hughd@...gle.com>, Baoquan He <bhe@...hat.com>, Nhat Pham <nphamcs@...il.com>, 
	Kemeng Shi <shikemeng@...weicloud.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>, 
	Ying Huang <ying.huang@...ux.alibaba.com>, Johannes Weiner <hannes@...xchg.org>, 
	David Hildenbrand <david@...hat.com>, Yosry Ahmed <yosryahmed@...gle.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Zi Yan <ziy@...dia.com>, 
	linux-kernel@...r.kernel.org, Kairui Song <kasong@...cent.com>
Subject: Re: [PATCH v4 01/15] docs/mm: add document for swap table

On Thu, Sep 18, 2025 at 3:03 PM Chris Li <chrisl@...nel.org> wrote:
>
> Hi Barry,
>
> How about this:
>
> A swap table stores one cluster worth of swap cache values, which is
> exactly one page table page on most morden 64 bit systems. This is not
> coincidental because the cluster size is determined by the huge page size.

I’d phrase it as “PMD huge page,” since we also have “PUD huge page.”

> The swap table is holding an array of pointers, which have the same
> size as the PTE. The size of the swap table should match the page table
> page.
>

I’m not entirely sure what you mean by “page table page.”
My understanding is that you’re saying:
The swap table contains an array of pointers, each the same size as a PTE,
so its total size typically matches a PTE page table—one page on modern
64-bit systems.

> If that sounds OK, I will send an incremental patch to Andrew.
>
> Chris

Thanks
Barry