From patchwork Fri Sep 23 13:12:34 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Robert Hoo X-Patchwork-Id: 9348077 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E927A607F2 for ; Fri, 23 Sep 2016 13:13:55 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DA9392A923 for ; Fri, 23 Sep 2016 13:13:55 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CDFDD2AAD9; Fri, 23 Sep 2016 13:13:55 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4EA722A923 for ; Fri, 23 Sep 2016 13:13:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759565AbcIWNNn (ORCPT ); Fri, 23 Sep 2016 09:13:43 -0400 Received: from mga03.intel.com ([134.134.136.65]:9252 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758394AbcIWNNg (ORCPT ); Fri, 23 Sep 2016 09:13:36 -0400 Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga103.jf.intel.com with ESMTP; 23 Sep 2016 06:13:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,381,1470726000"; d="scan'208";a="12584476" Received: from unknown (HELO localhost.localdomain.sh.intel.com) ([10.239.13.216]) by orsmga005.jf.intel.com with ESMTP; 23 Sep 2016 06:13:32 -0700 From: Robert Ho To: pbonzini@redhat.com, akpm@linux-foundation.org, mhocko@suse.com, oleg@redhat.com, dan.j.williams@intel.com, dave.hansen@intel.com Cc: guangrong.xiao@linux.intel.com, gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stefanha@redhat.com, yuhuang@redhat.com, linux-mm@kvack.org, ross.zwisler@linux.intel.com, robert.hu@intel.com Subject: [PATCH v3 2/2] Documentation/filesystems/proc.txt: Add more description for maps/smaps Date: Fri, 23 Sep 2016 21:12:34 +0800 Message-Id: <1474636354-25573-2-git-send-email-robert.hu@intel.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1474636354-25573-1-git-send-email-robert.hu@intel.com> References: <1474636354-25573-1-git-send-email-robert.hu@intel.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add some more description on the limitations for smaps/maps readings, as well as some guaruntees we can make. Signed-off-by: Robert Ho --- Documentation/filesystems/proc.txt | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 68080ad..90eabc7 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -515,6 +515,14 @@ be vanished or the reverse -- new added. This file is only present if the CONFIG_MMU kernel configuration option is enabled. +Note: for both /proc/PID/maps and /proc/PID/smaps readings, it's +possible in race conditions, that the mappings printed may not be that +up-to-date, because during each read walking, the task's mappings may have +changed, this typically happens in multithread cases. But anyway in each single +read these can be guarunteed: 1) the mapped addresses doesn't go backward; 2) no +overlaps 3) if there is something at a given vaddr during the entirety of the +life of the smaps/maps walk, there will be some output for it. + The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG bits on both physical and virtual pages associated with a process, and the soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).