Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754686AbbGXSSk (ORCPT ); Fri, 24 Jul 2015 14:18:40 -0400 Received: from mail-la0-f49.google.com ([209.85.215.49]:35670 "EHLO mail-la0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752532AbbGXSSi (ORCPT ); Fri, 24 Jul 2015 14:18:38 -0400 MIME-Version: 1.0 In-Reply-To: <20150721081755.GD4490@hori1.linux.bs1.fc.nec.co.jp> References: <20150714152516.29844.69929.stgit@buzz> <20150714153749.29844.81954.stgit@buzz> <20150721081755.GD4490@hori1.linux.bs1.fc.nec.co.jp> Date: Fri, 24 Jul 2015 19:18:37 +0100 Message-ID: Subject: Re: [PATCH v4 5/5] pagemap: add mmap-exclusive bit for marking pages mapped only here From: Mark Williamson To: Naoya Horiguchi Cc: Konstantin Khlebnikov , "linux-mm@kvack.org" , Andrew Morton , "Kirill A. Shutemov" , "linux-kernel@vger.kernel.org" , "linux-api@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1576 Lines: 32 Reviewed-by: Mark Williamson On Tue, Jul 21, 2015 at 9:17 AM, Naoya Horiguchi wrote: > On Tue, Jul 14, 2015 at 06:37:49PM +0300, Konstantin Khlebnikov wrote: >> This patch sets bit 56 in pagemap if this page is mapped only once. >> It allows to detect exclusively used pages without exposing PFN: >> >> present file exclusive state >> 0 0 0 non-present >> 1 1 0 file page mapped somewhere else >> 1 1 1 file page mapped only here >> 1 0 0 anon non-CoWed page (shared with parent/child) >> 1 0 1 anon CoWed page (or never forked) >> >> CoWed pages in (MAP_FILE | MAP_PRIVATE) areas are anon in this context. >> >> MMap-exclusive bit doesn't reflect potential page-sharing via swapcache: >> page could be mapped once but has several swap-ptes which point to it. >> Application could detect that by swap bit in pagemap entry and touch >> that pte via /proc/pid/mem to get real information. >> >> Signed-off-by: Konstantin Khlebnikov >> Requested-by: Mark Williamson >> Link: http://lkml.kernel.org/r/CAEVpBa+_RyACkhODZrRvQLs80iy0sqpdrd0AaP_-tgnX3Y9yNQ@mail.gmail.com > > Reviewed-by: Naoya Horiguchi -- 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/