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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 519554001B X-Stat-Signature: dhcjc9ps4e6rhjic99prdhzwjnqtnemt X-HE-Tag: 1689608962-146807 X-HE-Meta: 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 K0hf01pX SgBETUOsJRWjGKicG/UuxAm3J5D2UIEe0M+/ZVg73RYUvMNNKJZBZuhP3R5JqrCEb2/46HQ5lf4GP9e0g6wRkgEQ25RRnfx2ZKyHoxJdNWKMe+vyVneqEbFw7QfcHmy7TzzDvj2vN7HAGIfZ1Vmjb5I/EJeybGjepnMFK 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: On 17/07/2023 16:07, Matthew Wilcox wrote: > On Mon, Jul 17, 2023 at 03:31:09PM +0100, Ryan Roberts wrote: >> +/* >> + * folio_remove_rmap_range - take down pte mappings from a range of pages >> + * belonging to a folio. All pages are accounted as small pages. >> + * @folio: folio that all pages belong to >> + * @page: first page in range to remove mapping from >> + * @nr: number of pages in range to remove mapping from >> + * @vma: the vm area from which the mapping is removed >> + * >> + * The caller needs to hold the pte lock. >> + */ > > This could stand a little reworking. How about this? > > /** > * folio_remove_rmap_range - Take down PTE mappings from a range of pages. > * @folio: Folio containing all pages in range. > * @page: First page in range to unmap. > * @nr: Number of pages to unmap. > * @vma: The VM area containing the range. > * > * All pages in the range must belong to the same VMA & folio. They > * must be mapped with PTEs, not a PMD. > * > * Context: Caller holds the pte lock. > */ LGTM! thanks. > >> +void folio_remove_rmap_range(struct folio *folio, struct page *page, >> + int nr, struct vm_area_struct *vma) >> +{ >> + atomic_t *mapped = &folio->_nr_pages_mapped; >> + int nr_unmapped = 0; >> + int nr_mapped; >> + bool last; >> + enum node_stat_item idx; >> + >> + if (unlikely(folio_test_hugetlb(folio))) { >> + VM_WARN_ON_FOLIO(1, folio); >> + return; >> + } >> + >> + if (!folio_test_large(folio)) { >> + /* Is this the page's last map to be removed? */ >> + last = atomic_add_negative(-1, &page->_mapcount); >> + nr_unmapped = last; >> + } else { >> + for (; nr != 0; nr--, page++) { >> + /* Is this the page's last map to be removed? */ >> + last = atomic_add_negative(-1, &page->_mapcount); >> + if (last) { >> + /* Page still mapped if folio mapped entirely */ >> + nr_mapped = atomic_dec_return_relaxed(mapped); > > We're still doing one atomic op per page on the folio's nr_pages_mapped > ... is it possible to batch this and use atomic_sub_return_relaxed()? Good spot, something like this: } else { for (; nr != 0; nr--, page++) { /* Is this the page's last map to be removed? */ last = atomic_add_negative(-1, &page->_mapcount); if (last) nr_unmapped++; } /* Pages still mapped if folio mapped entirely */ nr_mapped = atomic_sub_return_relaxed(nr_unmapped, mapped); if (nr_mapped >= COMPOUND_MAPPED) nr_unmapped = 0; }