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authorRobert Ho <[email protected]>2016-10-07 17:02:39 -0700
committerLinus Torvalds <[email protected]>2016-10-07 18:46:30 -0700
commit53aeee7a86620b4dca81f6b807b37f36e7f99b09 (patch)
treeefb5845f22a175eb91323c968605636326b49545
parent855af072b6c40aeb266f4dc98fd9a6a49edf22af (diff)
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/[email protected] Signed-off-by: Robert Ho <[email protected]> Acked-by: Michal Hocko <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Xiao Guangrong <[email protected]> Cc: Robert Hu <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Dan Williams <[email protected]> Cc: Gleb Natapov <[email protected]> Cc: Marcelo Tosatti <[email protected]> Cc: Stefan Hajnoczi <[email protected]> Cc: Ross Zwisler <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
-rw-r--r--Documentation/filesystems/proc.txt12
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index fcc1ac094282..219ffd41a911 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).