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 90DBE3376A9 for ; Mon, 2 Mar 2026 09:08:04 +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=1772442484; cv=none; b=KzDAjtIUlpHH0FLpqP5350ytvC7VK/Bm0ee/UXuIBXOSLMdlfMWr8PChk5iWK+R4BZPzEIqrqeT6z0czsZKQrbP9ZjCsT30W+IlswfJ6PEdvb2oJTzoDSDlnq48rFXFB/qDflOf5wNeJQMvM5SGAxMSfyKqq4FzKKLMtmwr/8E8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772442484; c=relaxed/simple; bh=WKix1w6VLBg/gDg4vRJkY+zCH4JxsvUzp+EQmAzwonY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NQLkw0mlPC2RQWrIQ9ncg50n9WrZkhrY+1uyRhhQTnxZif0wh+pQLvw4XJ+qKa2LbtGYwIjSxe6tGTuJPupBFfQo7CEdFElPIhNZXEE4CpC1+SQXJo5wpp16hREMHbuBJE9oHDD2JmOiMMoOnzJN6aqs7mkoAD9gUUNJifEW5Jc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fxdegIGr; 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="fxdegIGr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E12D2C19423; Mon, 2 Mar 2026 09:07:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772442484; bh=WKix1w6VLBg/gDg4vRJkY+zCH4JxsvUzp+EQmAzwonY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fxdegIGrNkd+cX69aJMFxp0N5Zvug5H74CNpP97ZzYvt9YRpInSubQ5GWJkZ71rTX lNT7GYrcfaDXCfN10BeRSSsNGMy+o89TQjbMDhh9oZZP1rK4QN+3hyOPVfaDuJtylO m4eQDfzM10HN85HDJT9qwHfGc4DESRK5dVX+vrSfxIxW+A+v4DOnbQmPw0LQ9upPln 2DH+gISXJIyzKWXs0LmrLBKr8dugdDbNC/zja84rqdQvqtTkeZI7mHD5j/QEnru5oS CHcVMS2f8y4HU1adWcYPFuU3/9+sfOb+0RYp5WuSdkeNRiRsYZYlFjP23iGb3Uus3J Q5sLtB7fcxjdw== Message-ID: Date: Mon, 2 Mar 2026 10:07:55 +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> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit 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 ... What happened to using a boolen as return type and for "int young"? > +{ > + int young = 0; > + > + for (;;) { > + young |= ptep_test_and_clear_young(vma, addr, ptep); > + if (--nr == 0) > + break; > + ptep++; > + addr += PAGE_SIZE; > + } > + > + return young; > +} > +#endif -- Cheers, David