Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932930AbbKEJZI (ORCPT ); Thu, 5 Nov 2015 04:25:08 -0500 Received: from mail-wi0-f178.google.com ([209.85.212.178]:37405 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756598AbbKEJZD (ORCPT ); Thu, 5 Nov 2015 04:25:03 -0500 Date: Thu, 5 Nov 2015 11:24:59 +0200 From: "Kirill A. Shutemov" To: Vladimir Davydov Cc: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli , Hugh Dickins , Naoya Horiguchi , Sasha Levin , Minchan Kim , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new THP refcounting Message-ID: <20151105092459.GC7614@node.shutemov.name> References: <1446564375-72143-1-git-send-email-kirill.shutemov@linux.intel.com> <1446564375-72143-5-git-send-email-kirill.shutemov@linux.intel.com> <20151105091013.GC29259@esperanza> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151105091013.GC29259@esperanza> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2822 Lines: 96 On Thu, Nov 05, 2015 at 12:10:13PM +0300, Vladimir Davydov wrote: > On Tue, Nov 03, 2015 at 05:26:15PM +0200, Kirill A. Shutemov wrote: > ... > > @@ -56,23 +56,69 @@ static int page_idle_clear_pte_refs_one(struct page *page, > > { > > struct mm_struct *mm = vma->vm_mm; > > spinlock_t *ptl; > > + pgd_t *pgd; > > + pud_t *pud; > > pmd_t *pmd; > > pte_t *pte; > > bool referenced = false; > > > > - if (unlikely(PageTransHuge(page))) { > > - pmd = page_check_address_pmd(page, mm, addr, &ptl); > > - if (pmd) { > > - referenced = pmdp_clear_young_notify(vma, addr, pmd); > > + pgd = pgd_offset(mm, addr); > > + if (!pgd_present(*pgd)) > > + return SWAP_AGAIN; > > + pud = pud_offset(pgd, addr); > > + if (!pud_present(*pud)) > > + return SWAP_AGAIN; > > + pmd = pmd_offset(pud, addr); > > + > > + if (pmd_trans_huge(*pmd)) { > > + ptl = pmd_lock(mm, pmd); > > + if (!pmd_present(*pmd)) > > + goto unlock_pmd; > > + if (unlikely(!pmd_trans_huge(*pmd))) { > > spin_unlock(ptl); > > + goto map_pte; > > } > > + > > + if (pmd_page(*pmd) != page) > > + goto unlock_pmd; > > + > > + referenced = pmdp_clear_young_notify(vma, addr, pmd); > > + spin_unlock(ptl); > > + goto found; > > +unlock_pmd: > > + spin_unlock(ptl); > > + return SWAP_AGAIN; > > } else { > > - pte = page_check_address(page, mm, addr, &ptl, 0); > > - if (pte) { > > - referenced = ptep_clear_young_notify(vma, addr, pte); > > - pte_unmap_unlock(pte, ptl); > > - } > > + pmd_t pmde = *pmd; > > + barrier(); > > + if (!pmd_present(pmde) || pmd_trans_huge(pmde)) > > + return SWAP_AGAIN; > > + > > + } > > +map_pte: > > + pte = pte_offset_map(pmd, addr); > > + if (!pte_present(*pte)) { > > + pte_unmap(pte); > > + return SWAP_AGAIN; > > } > > + > > + ptl = pte_lockptr(mm, pmd); > > + spin_lock(ptl); > > + > > + if (!pte_present(*pte)) { > > + pte_unmap_unlock(pte, ptl); > > + return SWAP_AGAIN; > > + } > > + > > + /* THP can be referenced by any subpage */ > > + if (pte_pfn(*pte) - page_to_pfn(page) >= hpage_nr_pages(page)) { > > + pte_unmap_unlock(pte, ptl); > > + return SWAP_AGAIN; > > + } > > + > > + referenced = ptep_clear_young_notify(vma, addr, pte); > > + pte_unmap_unlock(pte, ptl); > > +found: > > Can't we hide this stuff in a helper function, which would be used by > both page_referenced_one and page_idle_clear_pte_refs_one, instead of > duplicating page_referenced_one code here? I would like to, but there's no obvious way to do that: PMDs and PTEs require different handling. Any ideas? -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/