linux-kernel - Re: [PATCH v5 1/5] mm: rmap: support batched checks of the references for large folios

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Message-ID: <aV321zAn3xRhkBRt@hyeyoo>
Date: Wed, 7 Jan 2026 15:01:59 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, david@...nel.org, catalin.marinas@....com,
        will@...nel.org, lorenzo.stoakes@...cle.com, ryan.roberts@....com,
        Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org,
        surenb@...gle.com, mhocko@...e.com, riel@...riel.com, jannh@...gle.com,
        willy@...radead.org, baohua@...nel.org, dev.jain@....com,
        linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/5] mm: rmap: support batched checks of the
 references for large folios

On Fri, Dec 26, 2025 at 02:07:55PM +0800, Baolin Wang wrote:
> Currently, folio_referenced_one() always checks the young flag for each PTE
> sequentially, which is inefficient for large folios. This inefficiency is
> especially noticeable when reclaiming clean file-backed large folios, where
> folio_referenced() is observed as a significant performance hotspot.
> 
> Moreover, on Arm64 architecture, which supports contiguous PTEs, there is already
> an optimization to clear the young flags for PTEs within a contiguous range.
> However, this is not sufficient. We can extend this to perform batched operations
> for the entire large folio (which might exceed the contiguous range: CONT_PTE_SIZE).
> 
> Introduce a new API: clear_flush_young_ptes() to facilitate batched checking
> of the young flags and flushing TLB entries, thereby improving performance
> during large folio reclamation. And it will be overridden by the architecture
> that implements a more efficient batch operation in the following patches.
> 
> While we are at it, rename ptep_clear_flush_young_notify() to
> clear_flush_young_ptes_notify() to indicate that this is a batch operation.
> 
> Reviewed-by: Ryan Roberts <ryan.roberts@....com>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---

Looks good to me, so:
Reviewed-by: Harry Yoo <harry.yoo@...cle.com>

-- 
Cheers,
Harry / Hyeonggon