Hey, While looking at ZONE_DEVICE struct page reuse particularly the last patch[0], I found two possible improvements for follow_hugetlb_page() which is solely used for get_user_pages()/pin_user_pages().
The first patch batches page refcount updates while the second tidies up storing the subpages/vmas. Both together bring the cost of slow variant of gup() cost from ~87.6k usecs to ~5.8k usecs. libhugetlbfs tests seem to pass as well gup_test benchmarks with hugetlbfs vmas. v2: * switch from refs++ to ++refs; * add Mike's Rb on patch 1; * switch from page++ to mem_map_offset() on the second patch; [0] https://lore.kernel.org/linux-mm/[email protected]/ Joao Martins (2): mm/hugetlb: grab head page refcount once for group of subpages mm/hugetlb: refactor subpage recording include/linux/mm.h | 3 +++ mm/gup.c | 5 ++-- mm/hugetlb.c | 66 +++++++++++++++++++++++++++------------------- 3 files changed, 44 insertions(+), 30 deletions(-) -- 2.17.1
