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 voJP6ROq 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 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 Tue, Feb 10, 2026 at 06:58:37PM +0530, Dev Jain wrote: > > On 06/02/26 8:52 pm, Matthew Wilcox wrote: > > On Fri, Feb 06, 2026 at 07:26:48PM +0530, Dev Jain wrote: > >> We test the patch with the following userspace program. A shmem VMA of > >> 2M is created, and faulted in, with sysfs setting > >> hugepages-2048k/shmem_enabled = always, so that the pagecache is populated > >> with a 2M folio. Then, a 64K VMA is created, and we fault on each page. > >> Then, we do MADV_DONTNEED to zap the pagetable, so that we can fault again > >> in the next iteration. We measure the accumulated time taken during > >> faulting the VMA. > >> > >> On arm64, > >> > >> without patch: > >> Total time taken by inner loop: 4701721766 ns > >> > >> with patch: > >> Total time taken by inner loop: 516043507 ns > >> > >> giving a 9x improvement. > > It's nice that you can construct a test-case that shows improvement, but > > is there any real workload that benefits from this? > > I can try to measure this. But, I constructed that testcase to test the > code path, not to show a perf boost (although the boost is obvious enough > so why not show it). As I say in the description: > > "Align finish_fault with filemap_map_pages, and map as many pages as > possible, without crossing VMA/PMD/file boundaries." > > The patch should rather be seen as an extension to 19773df031bc > ("mm/fault: try to map the entire file folio in finish_fault()"). > The code which my patch removes, was added when the norm was to still > perform per-page fault, the argument being, RSS inflation. > > Perhaps I can polish the patch description so that it clearly mentions > what the objective is. > Can we make any new respin of this RFC please. I am especially not confident given the immediate syzbot etc. If it's a speculative thing without great justification the series should be RFC until such time the community decides it's worthwhile. Thanks, Lorenzo