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b=qVbsLwkGch7h/7HSMmGtaC3uNnBXdDP2+NYlx+NZvoOzV75V0RgnusAq9j7F+EQ8c UNqKNUwrfsqhcVbtnWBDbLku4fdFZKeHU6foHHcc7cONdL9uzvG9d3nh85PVEsnmpq Itt+ye8x4DFvGucFINKbdXeDEg/YV29W4Hr0Te3CJboNNQ3LgxGQq0v7XolbmHQUtR Vc5ZNeA2AYpdOr7fvj0pS39bCUy1HOTsr3NiT3fDgtAf0A0VGFJGSR+DCHcR5a1Agk c3BYc/1MYVCxQJ9w5vin0G1Tu3d2wi7vL/Al3Z/IDutB7v4fg6qnf2a3OeCtH51FbJ zXd2cojMJVA+Q== Message-ID: Date: Wed, 25 Mar 2026 15:58:36 +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: "Lorenzo Stoakes (Oracle)" Cc: Baolin Wang , Barry Song <21cnbao@gmail.com>, 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> <86f611cb-1292-44e4-b629-6503135d33ca@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-Rspam-User: X-Rspamd-Queue-Id: C48FD120004 X-Stat-Signature: cddfx6bjdjbrwxe4pe5rzkschqp6bsos X-Rspamd-Server: rspam06 X-HE-Tag: 1774450725-700129 X-HE-Meta: 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 HvgKfDoU F/ipqLewaSXB2teDG+k1Gz4WfEi53XnV7LpXcdaJQ7Rvh4vRqYVoSsjgMOYVak+JKLG1L9tKcilRicOTF2yabymIb1+uqhOenan0Uw1Mr7jPymB0z6vKlyHn7JhKOknAdjNPLWVjJ17YQY3V3Sw4JyALH5Vt53Hr8ILXCGWZmdVnNzHcg/+xlpyRceSZnT+DrmQpidvp5NJjM8ezqGwG84ywpNE/Kh04BDqmZwN4/SYTM/BlY1BeJWSHTeu2w2H/7+ppIPwn9EdhV0KZa5jqlCggX1lfogD+9kyBs Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/25/26 15:36, Lorenzo Stoakes (Oracle) wrote: > On Mon, Mar 16, 2026 at 03:15:18PM +0100, David Hildenbrand (Arm) wrote: >> On 3/16/26 07:25, Baolin Wang wrote: >>> >>> >>> >>> 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. > > Sorry unclear here - does the series need more work or does a follow up patch > need more work? Follow up! -- Cheers, David