From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CA765278161 for ; Tue, 10 Feb 2026 02:01:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770688875; cv=none; b=URuu5DvPFX5JurkwXG3VhdlrONYKQFeVpvYqn8qOpWSmxNqRnHXbSoscmV5jizpKNYl3/SgRULr1QFXuDO14nfRBxymMTgpfoVZwL02X++9jjWRSqg1o3SKqd+l+mfR1s+XFYMTQKgYLnWi9RYKa2HjV6QUZC6YP4uKmD+AN2Jw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770688875; c=relaxed/simple; bh=yJ1jl+TBDgCg4czHQq+MiVE0XpD1TZqQ+Vkn1x9WRgA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=osC4m7vyyFhysv+S33upEWaO7gIXFMEbMLxeK6pTPMmLwocUyTSLI5JR1GJ+Vz3CesphU8ROZhDU8uf/fwUmQQFfnRwMO4kEfVRqhDlPhi0mGwY3B/LUjLk9IFb56LxouHUMbuCghQOa5x7R75P9vWtfjxa4AWd4AGyn404tcdg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=yJ88OPX6; arc=none smtp.client-ip=115.124.30.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="yJ88OPX6" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1770688865; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=nQ50p2KNl3amfBot28o/Z8pfWvYK3Anb03Fg5LdckDw=; b=yJ88OPX6Hu8W1vO7ERxF/+DqEYqWuHChDH6C2qjAiAUdYJ9QJuTZuMnMiY6ehMuCeQGMTuQeQfjo1jHZLwIg5qq+Aqh4QQlAcgi+2HPcyq65XdVxmG3o0gnsLCtD73uj65L/URa0nvX09d+4c86pliKdSHp7ru/achaycnNdQqM= Received: from 30.74.144.109(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WyxHdcT_1770688862 cluster:ay36) by smtp.aliyun-inc.com; Tue, 10 Feb 2026 10:01:03 +0800 Message-ID: Date: Tue, 10 Feb 2026 10:01:02 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 0/5] support batch checking of references and unmapping for large folios To: Andrew Morton 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 References: <20260209175316.2ef64ee244599765a74a6975@linux-foundation.org> From: Baolin Wang In-Reply-To: <20260209175316.2ef64ee244599765a74a6975@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/10/26 9:53 AM, Andrew Morton wrote: > 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? Yes. After discussing with David[1], we believe the original patch is correct, so the 'fix' is unnecessary. [1] https://lore.kernel.org/all/280ae63e-d66e-438f-8045-6c870420fe76@linux.alibaba.com/ The following diff looks good to me. Thanks. > 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; > _