On 23.08.22 09:50, Baolin Wang wrote:
> Considering the pmd entries of a CONT-PMD hugetlb can not span on
> multiple PMDs, we can change to use the PMD page lock, which can
> be much finer grain that lock in the mm.
>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> ---
> include/linux/hugetlb.h | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 3a96f67..d4803a89 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -892,9 +892,17 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
> static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
> struct mm_struct *mm, pte_t *pte)
> {
> - VM_BUG_ON(huge_page_size(h) == PAGE_SIZE);
> + unsigned long hp_size = huge_page_size(h);
>
> - if (huge_page_size(h) == PMD_SIZE) {
> + VM_BUG_ON(hp_size == PAGE_SIZE);
> +
> + /*
> + * Considering CONT-PMD size hugetlb, since the CONT-PMD entry
> + * can not span multiple PMDs, then we can use the fine grained
> + * PMD page lock.
> + */
> + if (hp_size == PMD_SIZE ||
> + (hp_size > PMD_SIZE && hp_size < PUD_SIZE)) {
> return pmd_lockptr(mm, (pmd_t *) pte);
> } else if (huge_page_size(h) < PMD_SIZE) {
> unsigned long mask = ~(PTRS_PER_PTE * sizeof(pte_t) - 1);
Is there a measurable performance gain? IOW, do we really care?
--
Thanks,
David / dhildenb
