path: root/Documentation
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authorCyrill Gorcunov <gorcunov@openvz.org>2012-12-17 16:03:13 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-17 17:15:22 -0800
commit834f82e2aa9a8ede94b17b656329f850c1471514 (patch)
treedbd2a721c3b6b4c7d3cd5826a9ceb867158a1941 /Documentation
parent7b9a7ec565505699f503b4fcf61500dceb36e744 (diff)
procfs: add VmFlags field in smaps output
During c/r sessions we've found that there is no way at the moment to fetch some VMA associated flags, such as mlock() and madvise(). This leads us to a problem -- we don't know if we should call for mlock() and/or madvise() after restore on the vma area we're bringing back to life. This patch intorduces a new field into "smaps" output called VmFlags, where all set flags associated with the particular VMA is shown as two letter mnemonics. [ Strictly speaking for c/r we only need mlock/madvise bits but it has been said that providing just a few flags looks somehow inconsistent. So all flags are here now. ] This feature is made available on CONFIG_CHECKPOINT_RESTORE=n kernels, as other applications may start to use these fields. The data is encoded in a somewhat awkward two letters mnemonic form, to encourage userspace to be prepared for fields being added or removed in the future. [a.p.zijlstra@chello.nl: props to use for_each_set_bit] [sfr@canb.auug.org.au: props to use array instead of struct] [akpm@linux-foundation.org: overall redesign and simplification] [akpm@linux-foundation.org: remove unneeded braces per sfr, avoid using bloaty for_each_set_bit()] Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
1 files changed, 38 insertions, 2 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 3844d21d6ca..74cb394e688 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -142,7 +142,7 @@ Table 1-1: Process specific entries in /proc
pagemap Page table
stack Report full stack trace, enable via CONFIG_STACKTRACE
smaps a extension based on maps, showing the memory consumption of
- each mapping
+ each mapping and flags associated with it
For example, to get the status information of a process, all you have to do is
@@ -415,8 +415,9 @@ Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Locked: 374 kB
+VmFlags: rd ex mr mw me de
-The first of these lines shows the same information as is displayed for the
+the first of these lines shows the same information as is displayed for the
mapping in /proc/PID/maps. The remaining lines show the size of the mapping
(size), the amount of the mapping that is currently resident in RAM (RSS), the
process' proportional share of this mapping (PSS), the number of clean and
@@ -430,6 +431,41 @@ and a page is modified, the file page is replaced by a private anonymous copy.
"Swap" shows how much would-be-anonymous memory is also used, but out on
+"VmFlags" field deserves a separate description. This member represents the kernel
+flags associated with the particular virtual memory area in two letter encoded
+manner. The codes are the following:
+ rd - readable
+ wr - writeable
+ ex - executable
+ sh - shared
+ mr - may read
+ mw - may write
+ me - may execute
+ ms - may share
+ gd - stack segment growns down
+ pf - pure PFN range
+ dw - disabled write to the mapped file
+ lo - pages are locked in memory
+ io - memory mapped I/O area
+ sr - sequential read advise provided
+ rr - random read advise provided
+ dc - do not copy area on fork
+ de - do not expand area on remapping
+ ac - area is accountable
+ nr - swap space is not reserved for the area
+ ht - area uses huge tlb pages
+ nl - non-linear mapping
+ ar - architecture specific flag
+ dd - do not include area into core dump
+ mm - mixed map area
+ hg - huge page advise flag
+ nh - no-huge page advise flag
+ mg - mergable advise flag
+Note that there is no guarantee that every flag and associated mnemonic will
+be present in all further kernel releases. Things get changed, the flags may
+be vanished or the reverse -- new added.
This file is only present if the CONFIG_MMU kernel configuration option is