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Mon, 09 Feb 2026 22:07:45 +0800 From: Baolin Wang To: akpm@linux-foundation.org, david@kernel.org, catalin.marinas@arm.com, will@kernel.org Cc: lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, willy@infradead.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 5/5] mm: rmap: support batched unmapping for file large folios Date: Mon, 9 Feb 2026 22:07:28 +0800 Message-ID: X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: AD49C180004 X-Stat-Signature: hnpfrzd1o5zb49rje516tgfaajpibbo7 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1770646068-218047 X-HE-Meta: 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 fexd9Ukq DdS7yeyx8vNNoeiUyAV1X0mYIPArC/52f6U00MTkHHlkWBATBnN+r45aZ+Wu7DJa2fTskyhkzrzv92CYeKUvllxY1sixNr3/L0WXqubBEMUJWQflyV2FLzU0OTGF+OazcEI90YCFVvurtRKqg1stg4jqPOGramuFU8phit10WW2L/cbpduGKbFMy4kHKEGh6PFyJNm9J1FaeK8u+gBw1LWAI6tMnw6D7FGXHgeHa46AMERuGEdYlOAGPXa3YQOcHpGUoIb7MvGYowqQXBV0K4lvZO8whoYtCpgtWICbAtiZuBQDBOoEAIvPOqi0cmr726xyXHe+qziVTvpu3Go3kEESkemqduyEqRAWInlNVejMzDe1Da0IpAqxQmL8UGHC0oh6Xy X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 Reviewed-by: Ryan Roberts Acked-by: Barry Song Reviewed-by: Harry Yoo Signed-off-by: Baolin Wang --- mm/rmap.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 8807f8a7df28..43cb9ac6f523 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1945,12 +1945,16 @@ static inline unsigned int folio_unmap_pte_batch(struct folio *folio, end_addr = pmd_addr_end(addr, vma->vm_end); max_nr = (end_addr - addr) >> PAGE_SHIFT; - /* We only support lazyfree batching for now ... */ - if (!folio_test_anon(folio) || folio_test_swapbacked(folio)) + /* We only support lazyfree or file folios batching for now ... */ + if (folio_test_anon(folio) && folio_test_swapbacked(folio)) return 1; + if (pte_unused(pte)) return 1; + if (userfaultfd_wp(vma)) + return 1; + return folio_pte_batch(folio, pvmw->pte, pte, max_nr); } @@ -2313,7 +2317,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, * * See Documentation/mm/mmu_notifier.rst */ - dec_mm_counter(mm, mm_counter_file(folio)); + add_mm_counter(mm, mm_counter_file(folio), -nr_pages); } discard: if (unlikely(folio_test_hugetlb(folio))) { -- 2.47.3