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b=POnnUt0yg6asAn/zifiuUgLA8LbsgRMM4IXlot5xx+dMJgXHwFv0dqHys90sGVZAo zgy7nOIeGYEDN6IAQPVE5zL9mUVJdMum5Q9gPUboowt1dE1WjBPNbz7h3xRG49Ae0b ec3eBKlC5bL8h/UvEl4losmqkU1lCtpYsMTc4NFM= Date: Mon, 9 Feb 2026 17:53:16 -0800 From: Andrew Morton To: Baolin Wang Cc: david@kernel.org, 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, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 0/5] support batch checking of references and unmapping for large folios Message-Id: <20260209175316.2ef64ee244599765a74a6975@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: F0B2020007 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: s5prcprr3xwb731ekt9bydzz7sg77hn8 X-HE-Tag: 1770688398-60843 X-HE-Meta: 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 u2i4p+Yr 3rV+F8IzmUlhOwKaECa3ETXPnXkFoHLOxWy7yfZBaDpzIcr6Wp6VKCEf3o11o9g8PX4HnMFWjVHwHq5rIj1qFfhbWeXdupzxDnoBOKnlbAyxlL3kMV+GZ2QwDCmmz5Y2qF2FVJRFzknWztJ5xYvYbWLIyU2SYjDfSOBl0TlypXf+BInnOFh0F8+XepruIgC/q8DceHAp+Jtl3ahFNyJNTMAMrXmjAOYdb8I040Td8wSWLp/YYRbdeCV4GtKBhB/kqRn/+q6GupWoDVx5QZAWnFZ5YVulWjm6ojHTobwXPD1PjHZK4ohyyfTkMZvUV9kkzoVCOhgKOQ4bgvSM= 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: On Mon, 9 Feb 2026 22:07:23 +0800 Baolin Wang wrote: > 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. > Thanks, I updated mm.git to this version. Below is how v6 altered mm.git. I notice that this fix: https://lore.kernel.org/all/de141225-a0c1-41fd-b3e1-bcab09827ddd@linux.alibaba.com/T/#u was not carried forward. Was this deliberate? Also, regarding the 80-column tricks in folio_referenced_one(): we're allowed to do this ;) unsigned long end_addr; unsigned int max_nr; end_addr = pmd_addr_end(address, vma->vm_end); max_nr = (end_addr - address) >> PAGE_SHIFT; arch/arm64/include/asm/pgtable.h | 2 +- include/linux/pgtable.h | 16 ++++++++++------ mm/rmap.c | 9 +++------ 3 files changed, 14 insertions(+), 13 deletions(-) --- a/arch/arm64/include/asm/pgtable.h~b +++ a/arch/arm64/include/asm/pgtable.h @@ -1843,7 +1843,7 @@ static inline int clear_flush_young_ptes unsigned long addr, pte_t *ptep, unsigned int nr) { - if (likely(nr == 1 && !pte_valid_cont(__ptep_get(ptep)))) + if (likely(nr == 1 && !pte_cont(__ptep_get(ptep)))) return __ptep_clear_flush_young(vma, addr, ptep); return contpte_clear_flush_young_ptes(vma, addr, ptep, nr); --- a/include/linux/pgtable.h~b +++ a/include/linux/pgtable.h @@ -1070,8 +1070,8 @@ static inline void wrprotect_ptes(struct #ifndef clear_flush_young_ptes /** - * clear_flush_young_ptes - Clear the access bit and perform a TLB flush for PTEs - * that map consecutive pages of the same folio. + * clear_flush_young_ptes - Mark PTEs that map consecutive pages of the same + * folio as old and flush the TLB. * @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. @@ -1087,13 +1087,17 @@ static inline void wrprotect_ptes(struct * pages that belong to the same folio. The PTEs are all in the same PMD. */ static inline int clear_flush_young_ptes(struct vm_area_struct *vma, - unsigned long addr, pte_t *ptep, - unsigned int nr) + unsigned long addr, pte_t *ptep, unsigned int nr) { - int i, young = 0; + int young = 0; - for (i = 0; i < nr; ++i, ++ptep, addr += PAGE_SIZE) + for (;;) { young |= ptep_clear_flush_young(vma, addr, ptep); + if (--nr == 0) + break; + ptep++; + addr += PAGE_SIZE; + } return young; } --- a/mm/rmap.c~b +++ a/mm/rmap.c @@ -963,10 +963,8 @@ static bool folio_referenced_one(struct referenced++; } else if (pvmw.pte) { if (folio_test_large(folio)) { - unsigned long end_addr = - pmd_addr_end(address, vma->vm_end); - unsigned int max_nr = - (end_addr - address) >> PAGE_SHIFT; + unsigned long end_addr = pmd_addr_end(address, vma->vm_end); + unsigned int max_nr = (end_addr - address) >> PAGE_SHIFT; pte_t pteval = ptep_get(pvmw.pte); nr = folio_pte_batch(folio, pvmw.pte, @@ -974,8 +972,7 @@ static bool folio_referenced_one(struct } ptes += nr; - if (clear_flush_young_ptes_notify(vma, address, - pvmw.pte, nr)) + if (clear_flush_young_ptes_notify(vma, address, pvmw.pte, nr)) referenced++; /* Skip the batched PTEs */ pvmw.pte += nr - 1; _