On Fri, Oct 30, 2015 at 09:49:37AM -0700, Shaohua Li wrote:
> 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.
Actually, it was my TODO but I forgot it. :(
I fixed for new version.
Thanks for the pointing out.
>
> Thanks,
> Shaohua
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