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Date: Tue, 3 Nov 2015 09:10:49 +0900 From: Minchan Kim <minchan@...nel.org> To: Shaohua Li <shli@...nel.org> CC: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Michael Kerrisk <mtk.manpages@...il.com>, linux-api@...r.kernel.org, Hugh Dickins <hughd@...gle.com>, Johannes Weiner <hannes@...xchg.org>, zhangyanfei@...fujitsu.com, Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, Jason Evans <je@...com>, Daniel Micay <danielmicay@...il.com>, "Kirill A. Shutemov" <kirill@...temov.name>, Michal Hocko <mhocko@...e.cz>, yalin.wang2010@...il.com Subject: Re: [PATCH 1/8] mm: support madvise(MADV_FREE) 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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