linux-kernel - Re: [PATCH v5 5/5] mm: rmap: support batched unmapping for file large folios

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Message-ID: <aV4DPmDxOsrYAa7X@hyeyoo>
Date: Wed, 7 Jan 2026 15:54:54 +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 5/5] mm: rmap: support batched unmapping for file
 large folios

On Fri, Dec 26, 2025 at 02:07:59PM +0800, Baolin Wang wrote:
> Similar to folio_referenced_one(), we can apply batched unmapping for file
> large folios to optimize the performance of file folios reclamation.
> 
> Barry previously implemented batched unmapping for lazyfree anonymous large
> folios[1] and did not further optimize anonymous large folios or file-backed
> large folios at that stage. As for file-backed large folios, the batched
> unmapping support is relatively straightforward, as we only need to clear
> the consecutive (present) PTE entries for file-backed large folios.
>
> Performance testing:
> Allocate 10G clean file-backed folios by mmap() in a memory cgroup, and try to
> reclaim 8G file-backed folios via the memory.reclaim interface. I can observe
> 75% performance improvement on my Arm64 32-core server (and 50%+ improvement
> on my X86 machine) with this patch.
> 
> W/o patch:
> real    0m1.018s
> user    0m0.000s
> sys     0m1.018s
> 
> W/ patch:
> real	0m0.249s
> user	0m0.000s
> sys	0m0.249s
> 
> [1] https://lore.kernel.org/all/20250214093015.51024-4-21cnbao@gmail.com/T/#u
> Reviewed-by: Ryan Roberts <ryan.roberts@....com>
> Acked-by: Barry Song <baohua@...nel.org>
> 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