On Fri, Oct 30, 2015 at 04:01:37PM +0900, Minchan Kim wrote:
> +static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
> + unsigned long end, struct mm_walk *walk)
> +
> +{
> + struct mmu_gather *tlb = walk->private;
> + struct mm_struct *mm = tlb->mm;
> + struct vm_area_struct *vma = walk->vma;
> + spinlock_t *ptl;
> + pte_t *pte, ptent;
> + struct page *page;
> +
> + split_huge_page_pmd(vma, addr, pmd);
> + if (pmd_trans_unstable(pmd))
> + return 0;
> +
> + pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
> + arch_enter_lazy_mmu_mode();
> + for (; addr != end; pte++, addr += PAGE_SIZE) {
> + ptent = *pte;
> +
> + if (!pte_present(ptent))
> + continue;
> +
> + page = vm_normal_page(vma, addr, ptent);
> + if (!page)
> + continue;
> +
> + if (PageSwapCache(page)) {
> + if (!trylock_page(page))
> + continue;
> +
> + if (!try_to_free_swap(page)) {
> + unlock_page(page);
> + continue;
> + }
> +
> + ClearPageDirty(page);
> + unlock_page(page);
> + }
> +
> + /*
> + * Some of architecture(ex, PPC) don't update TLB
> + * with set_pte_at and tlb_remove_tlb_entry so for
> + * the portability, remap the pte with old|clean
> + * after pte clearing.
> + */
> + ptent = ptep_get_and_clear_full(mm, addr, pte,
> + tlb->fullmm);
> + ptent = pte_mkold(ptent);
> + ptent = pte_mkclean(ptent);
> + set_pte_at(mm, addr, pte, ptent);
> + tlb_remove_tlb_entry(tlb, pte, addr);
The orginal ptent might not be dirty. In that case, the tlb_remove_tlb_entry
is unnecessary, so please add a check. In practice, I saw more TLB flush with
FREE compared to DONTNEED because of this issue.
Thanks,
Shaohua
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