Re: [PATCH v6 5/5] mm: rmap: support batched unmapping for file large folios
From: "David Hildenbrand (Arm)" <david@kernel.org>
Date: 2026-02-09 15:31:23
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linux-mm, lkml
On 2/9/26 15:07, 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. Note that it's not ready to support batched unmapping for uffd case, so let's still fallback to per-page unmapping for the uffd case. 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 (local) Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: Barry Song <baohua@kernel.org> Reviewed-by: Harry Yoo <redacted> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org> -- Cheers, David