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b=Ehl7K/4rE1asXxBnk+ljYExLi38p1QY5H3JQPyU3Dw1aVS7AlxcjALQupCiBIbhK7 1XwxolSPpD2kzFv8Ve62pYgU2ezvRA70PlVSHqhsrj57EqZf26UdWCt+ylLwstzzcj mLAxBQf0BwgyX85q+y4HrWi0HolMOoyrhmhIDebh3oULdo5uid4NYYcdGGJIbXYYq+ b8Mdq17b/vt86HPndC0RdwQ26TSEnaW36fYjUJZj6xPEotLJD7x0DHO6L1MHOpTSqB MaBWZPAmmlrmDBl1Wp3uz/Ww7A2eHC5s38FLk4pgAgHm3UsU6SvNS2cGdxjWInlyPr Ir+GgF58W4yQQ== Date: Wed, 25 Mar 2026 14:36:43 +0000 From: "Lorenzo Stoakes (Oracle)" To: "David Hildenbrand (Arm)" 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 Subject: Re: [PATCH v6 1/5] mm: rmap: support batched checks of the references for large folios Message-ID: References: <12132694536834262062d1fb304f8f8a064b6750.1770645603.git.baolin.wang@linux.alibaba.com> <43831628-a00f-4292-9797-cb96a029bb00@kernel.org> <86f611cb-1292-44e4-b629-6503135d33ca@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <86f611cb-1292-44e4-b629-6503135d33ca@kernel.org> X-Rspamd-Queue-Id: 77C73140013 X-Stat-Signature: d7mdax4q74xso5bnnw9pqog8q1ebg7re X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1774449407-339272 X-HE-Meta: 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 4+x7bBD0 Zk50g8/tvgaR+Iw6et4Lel4TUhiwBwTraFq1X1axGHsEhUT/Tr+7/xKxLZX4JKO6P3pkv6v76DBw07rKmmeJqa7rKw+Z/8cbl32l3k77+1iGSTzgFnBpKZ5K28u5JqO7b90WtDfUOSpPQ5mwXm9a8MLzByl6S7LcVbzdpmTv9pMMhB7MbWat7oX+K6GV8zneTtQBe4kuO7Zs1prIFqHpbt1upc61L4sCcDgkv85g1QGvGUYU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 16, 2026 at 03:15:18PM +0100, David Hildenbrand (Arm) wrote: > 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. Sorry unclear here - does the series need more work or does a follow up patch need more work? As this is in mm-stable afaict. Thanks, Lorenzo > > -- > Cheers, > > David