On 20 Jul 2021, at 2:55, Huang Ying wrote:
> Before the commit c5b5a3dd2c1f ("mm: thp: refactor NUMA fault
> handling"), the TLB flushing is done in do_huge_pmd_numa_page() itself
> via flush_tlb_range().
>
> But after commit c5b5a3dd2c1f ("mm: thp: refactor NUMA fault
> handling"), the TLB flushing is done in migrate_pages() as in the
> following code path anyway.
>
> do_huge_pmd_numa_page
> migrate_misplaced_page
> migrate_pages
>
> So now, the TLB flushing code in do_huge_pmd_numa_page() becomes
> unnecessary. So the code is deleted in this patch to simplify the
> code. This is only code cleanup, there's no visible performance
> difference.
But we save a potential TLB flush here right? Maybe the if statement
is not a common case.
Anyway, LGTM, Thanks. Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
>
> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> Cc: Yang Shi <shy828301@xxxxxxxxx>
> Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
> Cc: Zi Yan <ziy@xxxxxxxxxx>
> ---
> mm/huge_memory.c | 26 --------------------------
> 1 file changed, 26 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index afff3ac87067..9f21e44c9030 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1440,32 +1440,6 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
> goto out;
> }
>
> - /*
> - * Since we took the NUMA fault, we must have observed the !accessible
> - * bit. Make sure all other CPUs agree with that, to avoid them
> - * modifying the page we're about to migrate.
> - *
> - * Must be done under PTL such that we'll observe the relevant
> - * inc_tlb_flush_pending().
> - *
> - * We are not sure a pending tlb flush here is for a huge page
> - * mapping or not. Hence use the tlb range variant
> - */
> - if (mm_tlb_flush_pending(vma->vm_mm)) {
> - flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
> - /*
> - * change_huge_pmd() released the pmd lock before
> - * invalidating the secondary MMUs sharing the primary
> - * MMU pagetables (with ->invalidate_range()). The
> - * mmu_notifier_invalidate_range_end() (which
> - * internally calls ->invalidate_range()) in
> - * change_pmd_range() will run after us, so we can't
> - * rely on it here and we need an explicit invalidate.
> - */
> - mmu_notifier_invalidate_range(vma->vm_mm, haddr,
> - haddr + HPAGE_PMD_SIZE);
> - }
> -
> pmd = pmd_modify(oldpmd, vma->vm_page_prot);
> page = vm_normal_page_pmd(vma, haddr, pmd);
> if (!page)
> --
> 2.30.2
—
Best Regards,
Yan, Zi
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