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Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by desiato.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w28j8-00000006vMD-218w for linux-arm-kernel@lists.infradead.org; Mon, 16 Mar 2026 14:15:28 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id DFAAB43C59; Mon, 16 Mar 2026 14:15:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 672A1C19421; Mon, 16 Mar 2026 14:15:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773670524; bh=AMYLIbC0XsyIeE592yVqLMzFEBrfw2qSx6eHBAsjStk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=BowH4afH8xNOvUvPXoGnX3QiYu8G73nqHWtCjBoZU+TFzL04LqlcQ1DpKNBrWW3FZ +QX4rLlHxR8sluW7mz9nTROilho5xtAEMDGtkUjYE8UicGlscjLRmfWhUjdjoyvy0h t4w8HKjV0QGMecNN40YAKUHsKE9rLtQGt6JspdvvYpstALRuhCUTjCTljy4MNEDoQT oVDVC2Ymws8d8S97UvIvVqQ0YJCKNcfOG23HdZNoUk3z+yrYp367/8xA5lpl/H0Hos g5XFzt2ffsv8ex0HQ3AFCpSv+PwNvKGJ+fVx9kQUco0SG9bhb13I7h9CngzrwMTuv+ QwRj/MDzncpYQ== Message-ID: <86f611cb-1292-44e4-b629-6503135d33ca@kernel.org> Date: Mon, 16 Mar 2026 15:15:18 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/5] mm: rmap: support batched checks of the references for large folios To: Baolin Wang , Barry Song <21cnbao@gmail.com> Cc: akpm@linux-foundation.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, dev.jain@arm.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <12132694536834262062d1fb304f8f8a064b6750.1770645603.git.baolin.wang@linux.alibaba.com> <43831628-a00f-4292-9797-cb96a029bb00@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260316_141526_919668_B59E3222 X-CRM114-Status: GOOD ( 13.87 ) 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 3/16/26 07:25, Baolin Wang wrote: > > > On 3/10/26 4:17 PM, David Hildenbrand (Arm) wrote: >> On 3/10/26 02:37, Baolin Wang wrote: >>> >>> >>> >>> I understand your point. I’m concerned that I can’t test this patch on >>> every architecture to validate the benefits. Anyway, let me try this on >>> my X86 machine first. >> >> In any case, please make that a follow-up patch :) > > Sure. However, after investigating RISC‑V and x86, I found that > ptep_clear_flush_young() does not flush the TLB on these architectures: > > int ptep_clear_flush_young(struct vm_area_struct *vma, >                unsigned long address, pte_t *ptep) > { >     /* >      * On x86 CPUs, clearing the accessed bit without a TLB flush >      * doesn't cause data corruption. [ It could cause incorrect >      * page aging and the (mistaken) reclaim of hot pages, but the >      * chance of that should be relatively low. ] >      * >      * So as a performance optimization don't flush the TLB when >      * clearing the accessed bit, it will eventually be flushed by >      * a context switch or a VM operation anyway. [ In the rare >      * event of it not getting flushed for a long time the delay >      * shouldn't really matter because there's no real memory >      * pressure for swapout to react to. ] >      */ >     return ptep_test_and_clear_young(vma, address, ptep); > } You'd probably want an arch helper then, that tells you whether a flush_tlb_range() after ptep_test_and_clear_young() is required. Or some special flush_tlb_range() helper. I agree that it requires more work. -- Cheers, David