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b=BnD9gwi0VQwGVJZwxlZQSOLmSOral2e3j++2mIQTX80noalI4x2J+rOnTVVsPd5ua bijGBS4S+PN15GS2dwJyCXUcUl1+I4PSqcUyBG4KMCANZt9ucF/XE1bBdhJZFUXPrB pmR3QfTDBIoNgVHkDUSxRCCuwFFvYbo0ARFItqVTCM999NZ04o69nLKszndiNSCW/o TGVS2SyH8n2FSXZNGDFHnW9gJal76Pf4kPiku88kYtICDUCIpfRbQJnZ1nNG+WqI7L 2xKtn/qdYmPNFLV6GbRerLsyg16lm2w2zUDlrMOn94GiYGx3bPLRGnrwyMZZpk5ata jBo6ZVd/Hp3iw== Date: Wed, 25 Mar 2026 15:06:26 +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: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 02EED1C000C X-Stat-Signature: zijhgjocohrfsjxf4aaghmex81rt1nx5 X-Rspam-User: X-HE-Tag: 1774451194-375532 X-HE-Meta: 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 SEWPEcBq WMEemUW9RkNcz3882c4PD7SFe3SFv+UPk2/lGEo+Xffu3JG8RR9015APOxokz6nAQ/K0DM4MXrsCtOZidH6nxFEEwOiwZt3U8ifh9VEge112KSBPOCnnKC6px+rf+rMp96o0o94lTmdccaYswbh+hdQDsHxgOaMSQmqtk5Yr04MDtslOd2h4l8UcRjXuimD58M7H4bS52qP7AY9aqrHTXAc8Yr4gjP9I87SxBmegx3RgEL2c= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 25, 2026 at 03:58:36PM +0100, David Hildenbrand (Arm) wrote: > 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! Ok good as in mm-stable now. Sadly means I don't get to review it but there we go. > > -- > Cheers, > > David Thanks, Lorenzo