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Mon, 09 Feb 2026 22:07:37 +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 0/5] support batch checking of references and unmapping for large folios Date: Mon, 9 Feb 2026 22:07:23 +0800 Message-ID: X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 1DCE6140013 X-Stat-Signature: jm46ape53w88br1at4webbbz4bhksyuy X-Rspam-User: X-HE-Tag: 1770646061-402281 X-HE-Meta: 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 wEAGy0/P COVr6qGkcmMzKVsol7sNl31tafmpxcdoiru7yIl0eMcvibU9XQQ2CHqGX7mvWOo8MXIHJgXRN6KSfoNbFP5vWCONlXLLHLPwrS0A5xP5P069Zkr0m01Dc4yyK+mn1WzkhKSM2Cbt/A9xudEhaHpLDjZINQPccrWhxqlSn02CrQo8c0lw6aAObtAJp4WdxwniexEGgvdzs+Geg1tL00FTA5rB1QBVp6cETN6grc/mFQoL6De0+sLCilTO9ITLQb7n34BeYDVYabInuo34= 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: 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 Arm 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). Similar to folio_referenced_one(), we can also apply batched unmapping for large file folios to optimize the performance of file folio reclamation. By supporting batched checking of the young flags, flushing TLB entries, and unmapping, I can observed a significant performance improvements in my performance tests for file folios reclamation. Please check the performance data in the commit message of each patch. Run stress-ng and mm selftests, no issues were found. Patch 1: Add a new generic batched PTE helper that supports batched checks of the references for large folios. Patch 2 - 3: Preparation patches. patch 4: Implement the Arm64 arch-specific clear_flush_young_ptes(). Patch 5: Support batched unmapping for file large folios. Changes from v5: - Collect reviewed tags from Ryan, Harry and David. Thanks. - Fix some coding style issues (per David). - Skip batched unmapping for uffd case, reported by Dev. Thanks. Changes from v4: - Fix passing the incorrect 'CONT_PTES' for non-batched APIs. - Rename ptep_clear_flush_young_notify() to clear_flush_young_ptes_notify() (per Ryan). - Fix some coding style issues (per Ryan). - Add reviewed tag from Ryan. Thanks. Changes from v3: - Fix using an incorrect parameter in ptep_clear_flush_young_notify() (per Liam). Changes from v2: - Rearrange the patch set (per Ryan). - Add pte_cont() check in clear_flush_young_ptes() (per Ryan). - Add a helper to do contpte block alignment (per Ryan). - Fix some coding style issues (per Lorenzo and Ryan). - Add more comments and update the commit message (per Lorenzo and Ryan). - Add acked tag from Barry. Thanks. Changes from v1: - Add a new patch to support batched unmapping for file large folios. - Update the cover letter Baolin Wang (5): mm: rmap: support batched checks of the references for large folios arm64: mm: factor out the address and ptep alignment into a new helper arm64: mm: support batch clearing of the young flag for large folios arm64: mm: implement the architecture-specific clear_flush_young_ptes() mm: rmap: support batched unmapping for file large folios arch/arm64/include/asm/pgtable.h | 23 ++++++++---- arch/arm64/mm/contpte.c | 62 ++++++++++++++++++++------------ include/linux/mmu_notifier.h | 9 ++--- include/linux/pgtable.h | 35 ++++++++++++++++++ mm/rmap.c | 38 ++++++++++++++++---- 5 files changed, 129 insertions(+), 38 deletions(-) -- 2.47.3