From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C4A98D6ACF1 for ; Thu, 18 Dec 2025 12:20:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=8gCsoRPXq8HBtgip3JToLrUCxpLycBpcDqFKAnkAsok=; b=3hTSgg6155EzCoCRMC9mP5stBi NIObnUDEpz576VxpVWWYeSCVAIZWRjkXfsPDPvxQUQMRZfY/OlHfE3quH4TgoTaBZc+dReRFsOG5X KfqOH7kZ0PWP9D3+lU48Qsu85f501apuGckL07+PuZuCyzRJw2uwCGjLKIxOKLrEVKRPiZuMIVzoD 4UF4xmGFIUE4XMg3dTlkndPN1n1hYNc1T6GPEyaUtyqGgogYIF8/uwCtAuX8xskB0h7C69PnNKdC4 ZwEaXMmjTnWbY6iqn3pgV17oDgyeifXM66yApbXiL1bQoRDVbGBwMSfI3lPemOAmuYFuy3C0L9/L5 67tzvT1A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vWCzW-00000008PxG-3Hy6; Thu, 18 Dec 2025 12:20:22 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vWCzS-00000008Pwh-3qaF for linux-arm-kernel@lists.infradead.org; Thu, 18 Dec 2025 12:20:20 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3F75EFEC; Thu, 18 Dec 2025 04:20:10 -0800 (PST) Received: from [10.1.39.180] (unknown [10.1.39.180]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 929F73F762; Thu, 18 Dec 2025 04:20:14 -0800 (PST) Message-ID: Date: Thu, 18 Dec 2025 12:20:13 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] arm64: mm: support batch clearing of the young flag for large folios Content-Language: en-GB To: Baolin Wang , akpm@linux-foundation.org, david@kernel.org, catalin.marinas@arm.com, will@kernel.org Cc: lorenzo.stoakes@oracle.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, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <1beaa7de-4b31-4f19-abee-83872f868e28@arm.com> <96c0adcc-abfd-4a44-be93-1c6bd7942d6d@linux.alibaba.com> From: Ryan Roberts In-Reply-To: <96c0adcc-abfd-4a44-be93-1c6bd7942d6d@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251218_042019_046941_4C748263 X-CRM114-Status: GOOD ( 25.00 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 18/12/2025 07:15, Baolin Wang wrote: > > > On 2025/12/17 23:43, Ryan Roberts wrote: >> Sorry I'm a bit late to the party... > > Never mind. It's not late and comments are always welcome :) > >> On 11/12/2025 08:16, Baolin Wang wrote: >>> Currently, contpte_ptep_test_and_clear_young() and >>> contpte_ptep_clear_flush_young() >>> only clear the young flag and flush TLBs for PTEs within the contiguous range. >>> To support batch PTE operations for other sized large folios in the following >>> patches, adding a new parameter to specify the number of PTEs. >>> >>> While we are at it, rename the functions to maintain consistency with other >>> contpte_*() functions. >>> >>> Signed-off-by: Baolin Wang >>> --- >>>   arch/arm64/include/asm/pgtable.h | 12 ++++----- >>>   arch/arm64/mm/contpte.c          | 44 ++++++++++++++++++++++---------- >>>   2 files changed, 37 insertions(+), 19 deletions(-) >>> >>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >>> index 0944e296dd4a..e03034683156 100644 >>> --- a/arch/arm64/include/asm/pgtable.h >>> +++ b/arch/arm64/include/asm/pgtable.h >>> @@ -1679,10 +1679,10 @@ extern void contpte_clear_full_ptes(struct mm_struct >>> *mm, unsigned long addr, >>>   extern pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm, >>>                   unsigned long addr, pte_t *ptep, >>>                   unsigned int nr, int full); >>> -extern int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, >>> -                unsigned long addr, pte_t *ptep); >>> -extern int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, >>> -                unsigned long addr, pte_t *ptep); >>> +extern int contpte_test_and_clear_young_ptes(struct vm_area_struct *vma, >>> +                unsigned long addr, pte_t *ptep, unsigned int nr); >>> +extern int contpte_clear_flush_young_ptes(struct vm_area_struct *vma, >>> +                unsigned long addr, pte_t *ptep, unsigned int nr); >> >> The "contpte_" functions are intended to be private to the arm64 arch and should >> be exposed via the generic APIs. But I don't see any generic batched API for >> this, so you're only actually able to pass CONT_PTES as nr. Perhaps you're >> planning to define "test_and_clear_young_ptes()" and "clear_flush_young_ptes()" >> in later patches? > > Right. This is a preparation patch, and will be used in patch 2. > >>>   extern void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, >>>                   pte_t *ptep, unsigned int nr); >>>   extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma, >>> @@ -1854,7 +1854,7 @@ static inline int ptep_test_and_clear_young(struct >>> vm_area_struct *vma, >>>       if (likely(!pte_valid_cont(orig_pte))) >>>           return __ptep_test_and_clear_young(vma, addr, ptep); >>>   -    return contpte_ptep_test_and_clear_young(vma, addr, ptep); >>> +    return contpte_test_and_clear_young_ptes(vma, addr, ptep, CONT_PTES); >>>   } >>>     #define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH >>> @@ -1866,7 +1866,7 @@ static inline int ptep_clear_flush_young(struct >>> vm_area_struct *vma, >>>       if (likely(!pte_valid_cont(orig_pte))) >>>           return __ptep_clear_flush_young(vma, addr, ptep); >>>   -    return contpte_ptep_clear_flush_young(vma, addr, ptep); >>> +    return contpte_clear_flush_young_ptes(vma, addr, ptep, CONT_PTES); >>>   } >>>     #define wrprotect_ptes wrprotect_ptes >>> diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c >>> index c0557945939c..19b122441be3 100644 >>> --- a/arch/arm64/mm/contpte.c >>> +++ b/arch/arm64/mm/contpte.c >>> @@ -488,8 +488,9 @@ pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm, >>>   } >>>   EXPORT_SYMBOL_GPL(contpte_get_and_clear_full_ptes); >>>   -int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, >>> -                    unsigned long addr, pte_t *ptep) >>> +int contpte_test_and_clear_young_ptes(struct vm_area_struct *vma, >>> +                    unsigned long addr, pte_t *ptep, >>> +                    unsigned int nr) >>>   { >>>       /* >>>        * ptep_clear_flush_young() technically requires us to clear the access >>> @@ -500,39 +501,56 @@ int contpte_ptep_test_and_clear_young(struct >>> vm_area_struct *vma, >>>        * having to unfold. >>>        */ >>>   +    unsigned long start = addr; >> >> Personally I wouldn't bother defining start - just reuse addr. You're >> incrementing start in the below loop, so it's more appropriate to call it addr >> anyway. > > OK. > >>> +    unsigned long end = start + nr * PAGE_SIZE; >>>       int young = 0; >>>       int i; >>>   -    ptep = contpte_align_down(ptep); >>> -    addr = ALIGN_DOWN(addr, CONT_PTE_SIZE); >>> +    if (pte_cont(__ptep_get(ptep + nr - 1))) >>> +        end = ALIGN(end, CONT_PTE_SIZE); >>>   -    for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) >>> -        young |= __ptep_test_and_clear_young(vma, addr, ptep); >>> +    if (pte_cont(__ptep_get(ptep))) { >>> +        start = ALIGN_DOWN(start, CONT_PTE_SIZE); >>> +        ptep = contpte_align_down(ptep); >>> +    } >>> + >>> +    nr = (end - start) / PAGE_SIZE; >>> +    for (i = 0; i < nr; i++, ptep++, start += PAGE_SIZE) >> >> Given you're now defining end, perhaps we don't need nr? >> >>     for (; addr != end; ptep++, addr += PAGE_SIZE) >>         young |= __ptep_test_and_clear_young(vma, addr, ptep); > > Yes, good point. > >>> +        young |= __ptep_test_and_clear_young(vma, start, ptep); >>>         return young; >>>   } >>> -EXPORT_SYMBOL_GPL(contpte_ptep_test_and_clear_young); >>> +EXPORT_SYMBOL_GPL(contpte_test_and_clear_young_ptes); >>>   -int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, >>> -                    unsigned long addr, pte_t *ptep) >>> +int contpte_clear_flush_young_ptes(struct vm_area_struct *vma, >>> +                unsigned long addr, pte_t *ptep, >>> +                unsigned int nr) >>>   { >>>       int young; >>>   -    young = contpte_ptep_test_and_clear_young(vma, addr, ptep); >>> +    young = contpte_test_and_clear_young_ptes(vma, addr, ptep, nr); >>>         if (young) { >>> +        unsigned long start = addr; >>> +        unsigned long end = start + nr * PAGE_SIZE; >>> + >>> +        if (pte_cont(__ptep_get(ptep + nr - 1))) >>> +            end = ALIGN(end, CONT_PTE_SIZE); >>> + >>> +        if (pte_cont(__ptep_get(ptep))) >>> +            start = ALIGN_DOWN(start, CONT_PTE_SIZE); >>> + >> >> We now have this pattern of expanding contpte blocks up and down in 3 places. >> Perhaps create a helper? > > Sounds reasonable. How about the following helper? > > static pte_t *contpte_align_addr_ptep(unsigned long *start, unsigned long *end, >                                         pte_t *ptep, unsigned int nr) > { >         unsigned long end_addr = *start + nr * PAGE_SIZE; > >         if (pte_cont(__ptep_get(ptep + nr - 1))) I think this is safe but calling it out to check; you're not checking that the pte is valid, so theoretically you could have a swap-entry here with whatever overlays the contiguous bit set. So then you would incorrectly extend. But I think it is safe because the expectation is that core-mm has already checked that the whole range is present? >                 *end = ALIGN(end_addr, CONT_PTE_SIZE); > >         if (pte_cont(__ptep_get(ptep))) { >                 *start = ALIGN_DOWN(*start, CONT_PTE_SIZE); >                 ptep = contpte_align_down(ptep); >         } > >         return ptep; > } Looks good.