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 102DC45948 for ; Tue, 3 Mar 2026 08:51:08 +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=1772527869; cv=none; b=S46M+8xHYdlAJ8WoMAmbggrN+kgNmIZEWlY3zXwJ28q/QYaEapI7CqeYpQmFgX16OPFhCZNV/TERrUcufUCqdSrDDRKr3FMzNmheuYcUwbTOV1K9BZxWU0MZLildpUCbregVvLYXRfGqrDOdqW4xs8J3I/pxLi2BceDcKEybuDc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772527869; c=relaxed/simple; bh=2CCAoaRCdOOyLTEd958HxZE4sWRmnIGbYscxtuURPiQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=oqF85E2qV6ET3eJaYkhTHTWM6XO7F4cqaMOCwhlONrj1934p/JLSE0p+4vu/F8PXC9mUI3feALRua9ufriKYwCqKPRuur1c41MwzxC/ZJW+HBebsQpfb2RLikFgqzIdxr3KVX8BWXTgEEumu2NdKBF++hN5nb9VOSDHmaxqOBOo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hPZBH363; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hPZBH363" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61B49C116C6; Tue, 3 Mar 2026 08:51:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772527868; bh=2CCAoaRCdOOyLTEd958HxZE4sWRmnIGbYscxtuURPiQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hPZBH363HLmLj6thg8VLMbt5F6oDAzNl0hSpABg5fw9njux/vr1PXcMuDb9x+cuXM dxnLFVTbFZu8tGxcfDHIPkB9TkB4CYiL0YzuWPjRAtIfyMrqAe3xr0vlICISY6Qpgq gN+MMYMul36QU4EGyX7NrZFptehV1Ap7O1GocBIjRmtAg9l+Jen9UdaW7CjFAsMeO7 PavCrC49ldHj4djWk58jWPz8yYcrQQJ6tooGkNIqiNGhK8EjpyVQr2eqejs000Uq8m OBxaLekIKbVoXpl4MKx7VHq5DFm9lisHMlRjdGmuTbVt4xKcN71Nkmv2HCSgTgiy6O w/JLid6+muIfg== Message-ID: Date: Tue, 3 Mar 2026 09:51:00 +0100 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 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> <7b4266c8-f885-44fb-b39b-aee38625980c@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: 8bit On 3/3/26 03:36, Baolin Wang wrote: > > > On 3/2/26 5:07 PM, David Hildenbrand (Arm) wrote: >> 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 ... > > Ah, yes, not sure why I missed this one :( > >> What happened to using a boolen as return type and for "int young"? > As I replied to you previously [1], I’d like to do this in a follow-up > patchset that converts all functions that check the young flag. Does > that sound OK to you? > > [1] https://lore.kernel.org/all/32c538ce-6af8-48a8-86fc- > d26ee253af54@linux.alibaba.com/ Oh, missed that. Works for me. -- Cheers, David