From mboxrd@z Thu Jan 1 00:00:00 1970 From: Minchan Kim Subject: Re: [PATCH 1/8] mm: support madvise(MADV_FREE) Date: Tue, 3 Nov 2015 09:10:49 +0900 Message-ID: <20151103001049.GC17906@bbox> References: <1446188504-28023-1-git-send-email-minchan@kernel.org> <1446188504-28023-2-git-send-email-minchan@kernel.org> <20151030164937.GA44946@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: In-Reply-To: <20151030164937.GA44946-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Content-Disposition: inline Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Shaohua Li Cc: Andrew Morton , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Michael Kerrisk , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Hugh Dickins , Johannes Weiner , zhangyanfei-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org, Rik van Riel , Mel Gorman , KOSAKI Motohiro , Jason Evans , Daniel Micay , "Kirill A. Shutemov" , Michal Hocko , yalin.wang2010-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org List-Id: linux-api@vger.kernel.org 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