Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752248AbcKGXcJ (ORCPT ); Mon, 7 Nov 2016 18:32:09 -0500 Received: from mail-pf0-f193.google.com ([209.85.192.193]:33463 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751662AbcKGXcH (ORCPT ); Mon, 7 Nov 2016 18:32:07 -0500 From: Naoya Horiguchi To: linux-mm@kvack.org Cc: "Kirill A. Shutemov" , Hugh Dickins , Andrew Morton , Dave Hansen , Andrea Arcangeli , Mel Gorman , Michal Hocko , Vlastimil Babka , Pavel Emelyanov , Zi Yan , Balbir Singh , linux-kernel@vger.kernel.org, Naoya Horiguchi , Naoya Horiguchi Subject: [PATCH v2 01/12] mm: x86: move _PAGE_SWP_SOFT_DIRTY from bit 7 to bit 6 Date: Tue, 8 Nov 2016 08:31:46 +0900 Message-Id: <1478561517-4317-2-git-send-email-n-horiguchi@ah.jp.nec.com> X-Mailer: git-send-email 2.7.0 In-Reply-To: <1478561517-4317-1-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1478561517-4317-1-git-send-email-n-horiguchi@ah.jp.nec.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1883 Lines: 39 pmd_present() checks _PAGE_PSE along with _PAGE_PRESENT to avoid false negative return when it races with thp spilt (during which _PAGE_PRESENT is temporary cleared.) I don't think that dropping _PAGE_PSE check in pmd_present() works well because it can hurt optimization of tlb handling in thp split. In the current kernel, bit 6 is not used in non-present format because nonlinear file mapping is obsolete, so let's move _PAGE_SWP_SOFT_DIRTY to that bit. Bit 7 is used as reserved (always clear), so please don't use it for other purpose. Signed-off-by: Naoya Horiguchi --- arch/x86/include/asm/pgtable_types.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git v4.9-rc2-mmotm-2016-10-27-18-27/arch/x86/include/asm/pgtable_types.h v4.9-rc2-mmotm-2016-10-27-18-27_patched/arch/x86/include/asm/pgtable_types.h index 8b4de22..89e88f1 100644 --- v4.9-rc2-mmotm-2016-10-27-18-27/arch/x86/include/asm/pgtable_types.h +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/arch/x86/include/asm/pgtable_types.h @@ -98,14 +98,14 @@ * Tracking soft dirty bit when a page goes to a swap is tricky. * We need a bit which can be stored in pte _and_ not conflict * with swap entry format. On x86 bits 6 and 7 are *not* involved - * into swap entry computation, but bit 6 is used for nonlinear - * file mapping, so we borrow bit 7 for soft dirty tracking. + * into swap entry computation, but bit 7 is used for thp migration, + * so we borrow bit 6 for soft dirty tracking. * * Please note that this bit must be treated as swap dirty page - * mark if and only if the PTE has present bit clear! + * mark if and only if the PTE/PMD has present bit clear! */ #ifdef CONFIG_MEM_SOFT_DIRTY -#define _PAGE_SWP_SOFT_DIRTY _PAGE_PSE +#define _PAGE_SWP_SOFT_DIRTY _PAGE_DIRTY #else #define _PAGE_SWP_SOFT_DIRTY (_AT(pteval_t, 0)) #endif -- 2.7.0