On Sat 01-10-16 12:42:38, Robert Ho wrote: > Add some more description on the limitations for smaps/maps readings, as well > as some guaruntees we can make. > > Changelog: > v2: > Adopt Dave Hansen's revision from v1 as the description. > > Signed-off-by: Robert Ho <robert.hu@xxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > Documentation/filesystems/proc.txt | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt > index 68080ad..daa096f 100644 > --- a/Documentation/filesystems/proc.txt > +++ b/Documentation/filesystems/proc.txt > @@ -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). > -- > 1.8.3.1 > -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>