From: Robert Ho <robert.hu@intel.com> 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 [thread overview] Message-ID: <1474636354-25573-2-git-send-email-robert.hu@intel.com> (raw) In-Reply-To: <1474636354-25573-1-git-send-email-robert.hu@intel.com> Add some more description on the limitations for smaps/maps readings, as well as some guaruntees we can make. Signed-off-by: Robert Ho <robert.hu@intel.com> --- 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). -- 1.8.3.1
WARNING: multiple messages have this Message-ID (diff)
From: Robert Ho <robert.hu@intel.com> 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 [thread overview] Message-ID: <1474636354-25573-2-git-send-email-robert.hu@intel.com> (raw) In-Reply-To: <1474636354-25573-1-git-send-email-robert.hu@intel.com> Add some more description on the limitations for smaps/maps readings, as well as some guaruntees we can make. Signed-off-by: Robert Ho <robert.hu@intel.com> --- 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). -- 1.8.3.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-09-23 13:13 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-09-23 13:12 [PATCH v3 1/2] mm, proc: Fix region lost in /proc/self/smaps Robert Ho 2016-09-23 13:12 ` Robert Ho 2016-09-23 13:12 ` Robert Ho [this message] 2016-09-23 13:12 ` [PATCH v3 2/2] Documentation/filesystems/proc.txt: Add more description for maps/smaps Robert Ho 2016-09-23 16:06 ` Dave Hansen 2016-09-23 16:06 ` Dave Hansen 2016-09-28 2:27 ` Robert Hu 2016-09-23 13:50 ` [PATCH v3 1/2] mm, proc: Fix region lost in /proc/self/smaps Michal Hocko 2016-09-23 13:50 ` Michal Hocko 2016-09-23 14:39 ` Michal Hocko 2016-09-23 14:39 ` Michal Hocko 2016-09-23 13:56 ` Oleg Nesterov 2016-09-23 13:56 ` Oleg Nesterov 2016-09-23 14:53 ` Michal Hocko 2016-09-23 14:53 ` Michal Hocko 2016-09-23 15:53 ` Oleg Nesterov 2016-09-23 15:53 ` Oleg Nesterov 2016-09-26 8:46 ` Michal Hocko 2016-09-26 8:46 ` Michal Hocko 2016-09-29 13:14 ` Robert Hu 2016-09-29 13:42 ` Michal Hocko 2016-09-29 13:42 ` Michal Hocko 2016-09-29 13:05 ` Robert Hu
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