From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 0408A35898 for ; Tue, 10 Feb 2026 01:53:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770688398; cv=none; b=QPmx4QvA1hwlxNZ+4mHWVrSspiDtH0zEFATthcqpA4Isx3M/XsNJF1+ZsiYGnU+du5oZkXUDe/d7PA304F20Il5BeJ75M4pGO7sjaVgw6lKpYgjzn69MH7y46szA9vVthcQUCUpWzF0STIiExhbcOmu0yHz1R55DlXQ/lBjPTdI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770688398; c=relaxed/simple; bh=VsCzRTzENQvdbYEZ9wbxc31//QaNgPdb2GF/3ORsK/c=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=Zpf4eB5rNG9z9NnEbz3DS4e08nTejpzGzMDdsQBbfbV/51z3NK4lhuZXtpyYnXYccVWV/rWAADGUeAkRQUG7KHIOElfUxo6gkGksn6E4AxKJn4tEmr1uqx6AzLOFAc20sBsug+1P5pNclrUSxlXUCI3HHvcDJeX+DYFJPTW1FME= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=POnnUt0y; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="POnnUt0y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5500C116C6; Tue, 10 Feb 2026 01:53:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1770688397; bh=VsCzRTzENQvdbYEZ9wbxc31//QaNgPdb2GF/3ORsK/c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; 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) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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; _