set_area_direct_map() always updates direct map alias permissions in single page increments. For HUGE_VMAP areas it's suboptimal. Not only the loop in set_area_direct_map() needlessly has more iterations (e.g times 512 on x86), but it also causes fragmentation of the direct map that could be avoided for the HUGE_VMAP areas populated with large pages. All pages in an area are always of the same order: either same-order large pages when VM_ALLOW_HUGE_VMAP is set and all huge pages were successfully allocated, or order-0 page when VM_ALLOW_HUGE_VMAP is cleared or when huge pages allocation fails and fallback path is taken. Instead of updating the direct map permissions for every order-0 page in an area, use the area's page_order as the loop increment and update the large pages in one call to set_direct_map_{invalid,default}_noflush(). Signed-off-by: Mike Rapoport (Microsoft) --- mm/vmalloc.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index fc7993db4152..11170d1ee5be 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3361,12 +3361,15 @@ static inline void set_area_direct_map(const struct vm_struct *area, int (*set_direct_map)(struct page *page, unsigned int nr)) { - unsigned long i; + unsigned int nr = (1U << vm_area_page_order(area)); + + for (unsigned long i = 0; i < area->nr_pages; i += nr) { + if (page_address(area->pages[i])) { + int err = set_direct_map(area->pages[i], nr); - /* HUGE_VMALLOC passes small pages to set_direct_map */ - for (i = 0; i < area->nr_pages; i++) - if (page_address(area->pages[i])) - set_direct_map(area->pages[i], 1); + WARN_ON_ONCE(err); + } + } } /* -- 2.53.0