linux-kernel - Re: [RFC PATCH] arm64: Kconfig: enable ARCH_WANTS_THP

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Message-ID: <aV_3fxlzwOSz8B0t@willie-the-truck>
Date: Thu, 8 Jan 2026 18:29:19 +0000
From: Will Deacon <will@...nel.org>
To: Barry Song <21cnbao@...il.com>
Cc: Weilin Tong <tongweilin@...ux.alibaba.com>,
	Catalin Marinas <catalin.marinas@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...nel.org>, linux-mm@...ck.org,
	baolin.wang@...ux.alibaba.com
Subject: Re: [RFC PATCH] arm64: Kconfig: enable ARCH_WANTS_THP_SWAP for all
 pagesizes

On Fri, Dec 26, 2025 at 07:52:44PM +1300, Barry Song wrote:
> On Fri, Dec 26, 2025 at 7:39 PM Weilin Tong
> <tongweilin@...ux.alibaba.com> wrote:
> >
> > Currently, ARCH_WANTS_THP_SWAP was limited to 4K page size ARM64 kernels, but
> > large folios requiring swapping also exist in other page size configurations
> > (e.g. 64K). Without this config, large folios in these kernels cannot be swapped
> > out.
> >
> > Here we enable ARCH_WANTS_THP_SWAP for all ARM64 page sizes.
> 
> I no longer recall why this was not enabled for sizes other than
> 4 KB in commit d0637c505f8a ("arm64: enable THP_SWAP for arm64"), but
> it appears to be fine, and the swap cluster size should also be
> more friendly to PMD alignment.

You seemed to be worried about I/O latency in your original post:

https://lore.kernel.org/all/20220524071403.128644-1-21cnbao@gmail.com/

Will