Commit 53aeee7a authored Oct 07, 2016 by Robert Ho Committed by Linus Torvalds Oct 07, 2016

Documentation/filesystems/proc.txt: add more description for maps/smaps

Add some more description on the limitations for smaps/maps readings, as
well as some guaruntees we can make.

Link: http://lkml.kernel.org/r/1475296958-27652-2-git-send-email-robert.hu@intel.com


Signed-off-by: Robert Ho <robert.hu@intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Cc: Robert Hu <robert.hu@intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 855af072

Documentation/filesystems/proc.txt

+12 −0

Original line number	Diff line number	Diff line
		@@ -515,6 +515,18 @@ be vanished or the reverse -- new added.
		This file is only present if the CONFIG_MMU kernel configuration option is
		enabled.

		Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
		output can be achieved only in the single read call).
		This typically manifests when doing partial reads of these files while the
		memory map is being modified. Despite the races, we do provide the following
		guarantees:

		1) The mapped addresses never go backwards, which implies no two
		regions will ever overlap.
		2) 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).