From 57edfcfd3419b4799353d8cbd6ce49da075cfdbd Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Wed, 28 Jun 2023 17:53:07 -0400 Subject: mm/gup: accelerate thp gup even for "pages != NULL" The acceleration of THP was done with ctx.page_mask, however it'll be ignored if **pages is non-NULL. The old optimization was introduced in 2013 in 240aadeedc4a ("mm: accelerate mm_populate() treatment of THP pages"). It didn't explain why we can't optimize the **pages non-NULL case. It's possible that at that time the major goal was for mm_populate() which should be enough back then. Optimize thp for all cases, by properly looping over each subpage, doing cache flushes, and boost refcounts / pincounts where needed in one go. This can be verified using gup_test below: # chrt -f 1 ./gup_test -m 512 -t -L -n 1024 -r 10 Before: 13992.50 ( +-8.75%) After: 378.50 (+-69.62%) Link: https://lkml.kernel.org/r/20230628215310.73782-6-peterx@redhat.com Signed-off-by: Peter Xu Reviewed-by: Lorenzo Stoakes Cc: Andrea Arcangeli Cc: David Hildenbrand Cc: Hugh Dickins Cc: James Houghton Cc: Jason Gunthorpe Cc: John Hubbard Cc: Kirill A . Shutemov Cc: Matthew Wilcox Cc: Mike Kravetz Cc: Mike Rapoport (IBM) Cc: Vlastimil Babka Cc: Yang Shi Signed-off-by: Andrew Morton --- mm/gup.c | 51 ++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 44 insertions(+), 7 deletions(-) (limited to 'mm') diff --git a/mm/gup.c b/mm/gup.c index d70f8f0613f4..59e182634ba8 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1282,16 +1282,53 @@ retry: goto out; } next_page: - if (pages) { - pages[i] = page; - flush_anon_page(vma, page, start); - flush_dcache_page(page); - ctx.page_mask = 0; - } - page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask); if (page_increm > nr_pages) page_increm = nr_pages; + + if (pages) { + struct page *subpage; + unsigned int j; + + /* + * This must be a large folio (and doesn't need to + * be the whole folio; it can be part of it), do + * the refcount work for all the subpages too. + * + * NOTE: here the page may not be the head page + * e.g. when start addr is not thp-size aligned. + * try_grab_folio() should have taken care of tail + * pages. + */ + if (page_increm > 1) { + struct folio *folio; + + /* + * Since we already hold refcount on the + * large folio, this should never fail. + */ + folio = try_grab_folio(page, page_increm - 1, + foll_flags); + if (WARN_ON_ONCE(!folio)) { + /* + * Release the 1st page ref if the + * folio is problematic, fail hard. + */ + gup_put_folio(page_folio(page), 1, + foll_flags); + ret = -EFAULT; + goto out; + } + } + + for (j = 0; j < page_increm; j++) { + subpage = nth_page(page, j); + pages[i + j] = subpage; + flush_anon_page(vma, subpage, start + j * PAGE_SIZE); + flush_dcache_page(subpage); + } + } + i += page_increm; start += page_increm * PAGE_SIZE; nr_pages -= page_increm; -- cgit v1.2.3