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b=hPZBH363HLmLj6thg8VLMbt5F6oDAzNl0hSpABg5fw9njux/vr1PXcMuDb9x+cuXM dxnLFVTbFZu8tGxcfDHIPkB9TkB4CYiL0YzuWPjRAtIfyMrqAe3xr0vlICISY6Qpgq gN+MMYMul36QU4EGyX7NrZFptehV1Ap7O1GocBIjRmtAg9l+Jen9UdaW7CjFAsMeO7 PavCrC49ldHj4djWk58jWPz8yYcrQQJ6tooGkNIqiNGhK8EjpyVQr2eqejs000Uq8m OBxaLekIKbVoXpl4MKx7VHq5DFm9lisHMlRjdGmuTbVt4xKcN71Nkmv2HCSgTgiy6O w/JLid6+muIfg== Message-ID: Date: Tue, 3 Mar 2026 09:51:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/6] mm: add a batched helper to clear the young flag for large folios To: Baolin Wang , akpm@linux-foundation.org Cc: catalin.marinas@arm.com, will@kernel.org, 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, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hannes@cmpxchg.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <589d743f4e048dc749002a7e1a1aec5d511c406b.1772185080.git.baolin.wang@linux.alibaba.com> <7b4266c8-f885-44fb-b39b-aee38625980c@linux.alibaba.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: B8A42C0012 X-Rspamd-Server: rspam07 X-Stat-Signature: wgp9qchgukngkq8hsac3hmnxnt61g87r X-Rspam-User: X-HE-Tag: 1772527869-772855 X-HE-Meta: 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 rs7egdST a5IwkXsRAJ2h6WEFwPEV7dgDJHNm6lHqvrCZiVvRDdloQwoEQTGO0OyVAdoW85eNMFILoWyXzvFtz0W0BCUsvJSt84OOGXxd35RnHsj5BYOTJvYpp448+fvctdTH5RDRkX9nt7Ma/PvowV/e9Aygm4ghzF/wnsl31gDafEUJbxrs1aYwtFV/9PNzfu+ydCN/DFMYJUifoMwvrtpTrWBDh/r3IwRKeQJmvWkdgkuzEuAaoeU5wu7oKvB2/AAAlDqt21nu77qyEeWHmoCBCbGYHH2wRFNnYJPGbZmIya/Cbt1Y4rT8aALlPwuaAzdAVKHtnzCVWvfJxMtqO+qgytG04oz7YL8eRMYdwlFeQWlWassa61jw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/3/26 03:36, Baolin Wang wrote: > > > On 3/2/26 5:07 PM, David Hildenbrand (Arm) wrote: >> On 2/27/26 10:44, Baolin Wang wrote: >>> Currently, MGLRU will call ptep_test_and_clear_young_notify() to >>> check and >>> clear the young flag for each PTE sequentially, which is inefficient for >>> large folios reclamation. >>> >>> Moreover, on Arm64 architecture, which supports contiguous PTEs, the >>> Arm64- >>> specific ptep_test_and_clear_young() already implements an >>> optimization to >>> clear the young flags for PTEs within a contiguous range. However, >>> this is not >>> sufficient. Similar to the Arm64 specific clear_flush_young_ptes(), >>> we can >>> extend this to perform batched operations for the entire large folio >>> (which >>> might exceed the contiguous range: CONT_PTE_SIZE). >>> >>> Thus, we can introduce a new batched helper: >>> test_and_clear_young_ptes() and >>> its wrapper test_and_clear_young_ptes_notify() which are consistent >>> with the >>> existing functions, to perform batched checking of the young flags >>> for large >>> folios, which can help improve performance during large folio >>> reclamation when >>> MGLRU is enabled. And it will be overridden by the architecture that >>> implements >>> a more efficient batch operation in the following patches. >>> >>> Signed-off-by: Baolin Wang >>> --- >>>   include/linux/pgtable.h | 38 ++++++++++++++++++++++++++++++++++++++ >>>   mm/internal.h           | 16 +++++++++++----- >>>   2 files changed, 49 insertions(+), 5 deletions(-) >>> >>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >>> index 776993d4567b..29bd9fd04e1e 100644 >>> --- a/include/linux/pgtable.h >>> +++ b/include/linux/pgtable.h >>> @@ -1103,6 +1103,44 @@ static inline int >>> clear_flush_young_ptes(struct vm_area_struct *vma, >>>   } >>>   #endif >>>   +#ifndef test_and_clear_young_ptes >>> +/** >>> + * test_and_clear_young_ptes - Mark PTEs that map consecutive pages >>> of the same >>> + *                   folio as old >>> + * @vma: The virtual memory area the pages are mapped into. >>> + * @addr: Address the first page is mapped at. >>> + * @ptep: Page table pointer for the first entry. >>> + * @nr: Number of entries to clear access bit. >>> + * >>> + * May be overridden by the architecture; otherwise, implemented as >>> a simple >>> + * loop over ptep_test_and_clear_young(). >>> + * >>> + * Note that PTE bits in the PTE range besides the PFN can differ. >>> For example, >>> + * some PTEs might be write-protected. >>> + * >>> + * Context: The caller holds the page table lock.  The PTEs map >>> consecutive >>> + * pages that belong to the same folio.  The PTEs are all in the >>> same PMD. >>> + * >>> + * Returns: whether any PTE was young. >>> + */ >>> +static inline int test_and_clear_young_ptes(struct vm_area_struct *vma, >>> +                        unsigned long addr, pte_t *ptep, >>> +                        unsigned int nr) >> >> Two tabs ... > > Ah, yes, not sure why I missed this one :( > >> What happened to using a boolen as return type and for "int young"? > As I replied to you previously [1], I’d like to do this in a follow-up > patchset that converts all functions that check the young flag. Does > that sound OK to you? > > [1] https://lore.kernel.org/all/32c538ce-6af8-48a8-86fc- > d26ee253af54@linux.alibaba.com/ Oh, missed that. Works for me. -- Cheers, David