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| author | Robert Ho <robert.hu@intel.com> | 2016-10-07 17:02:39 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-07 18:46:30 -0700 |
| commit | 53aeee7a86620b4dca81f6b807b37f36e7f99b09 (patch) | |
| tree | efb5845f22a175eb91323c968605636326b49545 /Documentation/filesystems/proc.txt | |
| parent | 855af072b6c40aeb266f4dc98fd9a6a49edf22af (diff) | |
| download | lwn-53aeee7a86620b4dca81f6b807b37f36e7f99b09.tar.gz lwn-53aeee7a86620b4dca81f6b807b37f36e7f99b09.zip | |
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>
Diffstat (limited to 'Documentation/filesystems/proc.txt')
| -rw-r--r-- | Documentation/filesystems/proc.txt | 12 |
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). |