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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: gmu43ie9efh69fmokpgcncj4ciumt7tx X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 3D8B480011 X-HE-Tag: 1750766609-257469 X-HE-Meta: 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 lvVQQQHF rIqdt687yg1PTp20P9YRVK6ab0KyaybaZ+qW5Y4SwQSbc0NlSX2FMnkTe8aDxxRcj0zJcQ3KtoU2t9xMHf+ySNvrXA17wHUEQEmJk9Xff/fXhObw2CgYr9tpiQsHZpac7j0IbHMqqN70OFPfjy7U6VICYlY3yN4v5H69AC3xABme+oRopQiRL1U6nCNRXMOlPFQaRnj93v0F8frir3Fa3/nW+WZ/ttthtaGAHD9fRoIejRBCIBKGonrYjJo8LCtWQ2O2jfEdfdsUuq9MiRcPns31FZ0Ny40UJSeJn+r1W8Q9bxqjpVRas3CaXUgWceUVL2xpMbWV2Y1+ZOvrMff4OzyeYnIvi07qhgMqnP7P5NVDGvjYK+dMjzVCNCMTVZQp2j5TIq1Xg33N6MTMfrTtfHsxqhTcsQ7D4yO1/Uaky3J1FCw3jJ9KIzHBgB2jqz/Gb4BfHJF0pH7dZJjrcq/jvnI0rug== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 24.06.25 14:00, Alexander Gordeev wrote: > On Tue, Jun 24, 2025 at 11:40:05AM +0200, David Hildenbrand wrote: >> On 24.06.25 11:37, Alexander Gordeev wrote: >>> On Mon, Jun 23, 2025 at 09:45:34PM +0200, David Hildenbrand wrote: >>> ... >>>> Let's ask the real questions: who checks PGTBL_PTE_MODIFIED? >>>> >>>> I see >>>> >>>> if (mask & ARCH_PAGE_TABLE_SYNC_MASK) >>>> arch_sync_kernel_mappings(start, start + size); >>>> >>>> And then >>>> >>>> arch/arm/include/asm/page.h:#define ARCH_PAGE_TABLE_SYNC_MASK PGTBL_PMD_MODIFIED >>>> arch/x86/include/asm/pgtable-2level_types.h:#define ARCH_PAGE_TABLE_SYNC_MASK PGTBL_PMD_MODIFIED >>>> arch/x86/include/asm/pgtable-3level_types.h:#define ARCH_PAGE_TABLE_SYNC_MASK PGTBL_PMD_MODIFIED >>>> >>>> >>>> Which makes me wonder why we need PGTBL_PTE_MODIFIED at all? Is there some other check I am missing? >>>> >>>> (same question regarding everything excepy PGTBL_PMD_MODIFIED, because that actually seems to be used) >>> >>> AFAICT it was thought as architecture-specific: >>> >>> /* >>> * Architectures can set this mask to a combination of PGTBL_P?D_MODIFIED values >>> * and let generic vmalloc and ioremap code know when arch_sync_kernel_mappings() >>> * needs to be called. >>> */ >>> #ifndef ARCH_PAGE_TABLE_SYNC_MASK >>> #define ARCH_PAGE_TABLE_SYNC_MASK 0 >>> #endif >>> >>> Not sure if that needs to be addressed at all. >> >> Okay, if there are no users of PGTBL_PTE_MODIFIED we could just ... remove >> it. Dead code. > > As you noticed, PGTBL_PMD_MODIFIED bit is used only. Thus, all other > bits would have to be removed as well, not just PGTBL_PTE_MODIFIED? Likely, yes. > > That is more or less revert of at least the below commits and rewriting > it in a PMD-focused manner: > > 2ba3e6947aed ("mm/vmalloc: track which page-table levels were modified") > d8626138009b ("mm: add functions to track page directory modifications") > > That would be a completely different effort, which I am not aming at ;) Well, I don't think we should be taking this micro-optimization patch here TBH. The real optimization is getting rid of dead code, not optimizing dead code. -- Cheers, David / dhildenb