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b=fxdegIGrNkd+cX69aJMFxp0N5Zvug5H74CNpP97ZzYvt9YRpInSubQ5GWJkZ71rTX lNT7GYrcfaDXCfN10BeRSSsNGMy+o89TQjbMDhh9oZZP1rK4QN+3hyOPVfaDuJtylO m4eQDfzM10HN85HDJT9qwHfGc4DESRK5dVX+vrSfxIxW+A+v4DOnbQmPw0LQ9upPln 2DH+gISXJIyzKWXs0LmrLBKr8dugdDbNC/zja84rqdQvqtTkeZI7mHD5j/QEnru5oS CHcVMS2f8y4HU1adWcYPFuU3/9+sfOb+0RYp5WuSdkeNRiRsYZYlFjP23iGb3Uus3J Q5sLtB7fcxjdw== Message-ID: Date: Mon, 2 Mar 2026 10:07:55 +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> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 781zxju98566yqs6k8tioydf8sjpx6jz X-Rspam-User: X-Rspamd-Queue-Id: 632AA120006 X-Rspamd-Server: rspam12 X-HE-Tag: 1772442485-149711 X-HE-Meta: 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 ... What happened to using a boolen as return type and for "int young"? > +{ > + int young = 0; > + > + for (;;) { > + young |= ptep_test_and_clear_young(vma, addr, ptep); > + if (--nr == 0) > + break; > + ptep++; > + addr += PAGE_SIZE; > + } > + > + return young; > +} > +#endif -- Cheers, David