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Subject[PATCH v5 6/6] mm, procfs: breakdown RSS for anon, shmem and file in /proc/pid/status
From: Jerome Marchand <>

There are several shortcomings with the accounting of shared memory (SysV shm,
shared anonymous mapping, mapping of a tmpfs file). The values in
/proc/<pid>/status and <...>/statm don't allow to distinguish between shmem
memory and a shared mapping to a regular file, even though theirs implication
on memory usage are quite different: during reclaim, file mapping can be
dropped or written back on disk, while shmem needs a place in swap.

Also, to distinguish the memory occupied by anonymous and file mappings, one
has to read the /proc/pid/statm file, which has a field for the file mappings
(again, including shmem) and total memory occupied by these mappings (i.e.
equivalent to VmRSS in the <...>/status file. Getting the value for anonymous
mappings only is thus not exactly user-friendly (the statm file is intended
to be rather efficiently machine-readable).

To address both of these shortcomings, this patch adds a breakdown of VmRSS in
/proc/<pid>/status via new fields RssAnon, RssFile and RssShmem, making use of
the previous preparatory patch. These fields tell the user the memory occupied
by private anonymous pages, mapped regular files and shmem, respectively.
Other existing fields in /status and /statm files are left without change.
The /statm file can be extended in the future, if there's a need for that.

Example (part of) /proc/pid/status output including the new Rss* fields:

VmPeak: 2001008 kB
VmSize: 2001004 kB
VmLck: 0 kB
VmPin: 0 kB
VmHWM: 5108 kB
VmRSS: 5108 kB
RssAnon: 92 kB
RssFile: 1324 kB
RssShmem: 3692 kB
VmData: 192 kB
VmStk: 136 kB
VmExe: 4 kB
VmLib: 1784 kB
VmPTE: 3928 kB
VmPMD: 20 kB
VmSwap: 0 kB
HugetlbPages: 0 kB

[ forward-porting, tweak changelog]
Signed-off-by: Jerome Marchand <>
Signed-off-by: Vlastimil Babka <>
Acked-by: Konstantin Khlebnikov <>
Acked-by: Michal Hocko <>
Acked-by: Hugh Dickins <>
Documentation/filesystems/proc.txt | 13 +++++++++++--
fs/proc/task_mmu.c | 14 ++++++++++++--
2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index fdeb5b3..ffcd495 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -169,6 +169,9 @@ For example, to get the status information of a process, all you have to do is
VmLck: 0 kB
VmHWM: 476 kB
VmRSS: 476 kB
+ RssAnon: 352 kB
+ RssFile: 120 kB
+ RssShmem: 4 kB
VmData: 156 kB
VmStk: 88 kB
VmExe: 68 kB
@@ -231,7 +234,12 @@ Table 1-2: Contents of the status files (as of 4.1)
VmSize total program size
VmLck locked memory size
VmHWM peak resident set size ("high water mark")
- VmRSS size of memory portions
+ VmRSS size of memory portions. It contains the three
+ following parts (VmRSS = RssAnon + RssFile + RssShmem)
+ RssAnon size of resident anonymous memory
+ RssFile size of resident file mappings
+ RssShmem size of resident shmem memory (includes SysV shm,
+ mapping of tmpfs and shared anonymous mappings)
VmData size of data, stack, and text segments
VmStk size of data, stack, and text segments
VmExe size of text segment
@@ -266,7 +274,8 @@ Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
Field Content
size total program size (pages) (same as VmSize in status)
resident size of memory portions (pages) (same as VmRSS in status)
- shared number of pages that are shared (i.e. backed by a file)
+ shared number of pages that are shared (i.e. backed by a file, same
+ as RssFile+RssShmem in status)
trs number of pages that are 'code' (not including libs; broken,
includes data segment)
lrs number of pages of library (always 0 on 2.6)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 19d190b..67aaaad 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -23,9 +23,13 @@

void task_mem(struct seq_file *m, struct mm_struct *mm)
- unsigned long data, text, lib, swap, ptes, pmds;
+ unsigned long data, text, lib, swap, ptes, pmds, anon, file, shmem;
unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;

+ anon = get_mm_counter(mm, MM_ANONPAGES);
+ file = get_mm_counter(mm, MM_FILEPAGES);
+ shmem = get_mm_counter(mm, MM_SHMEMPAGES);
* Note: to minimize their overhead, mm maintains hiwater_vm and
* hiwater_rss only when about to *lower* total_vm or rss. Any
@@ -36,7 +40,7 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
hiwater_vm = total_vm = mm->total_vm;
if (hiwater_vm < mm->hiwater_vm)
hiwater_vm = mm->hiwater_vm;
- hiwater_rss = total_rss = get_mm_rss(mm);
+ hiwater_rss = total_rss = anon + file + shmem;
if (hiwater_rss < mm->hiwater_rss)
hiwater_rss = mm->hiwater_rss;

@@ -53,6 +57,9 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
"VmPin:\t%8lu kB\n"
"VmHWM:\t%8lu kB\n"
"VmRSS:\t%8lu kB\n"
+ "RssAnon:\t%8lu kB\n"
+ "RssFile:\t%8lu kB\n"
+ "RssShmem:\t%8lu kB\n"
"VmData:\t%8lu kB\n"
"VmStk:\t%8lu kB\n"
"VmExe:\t%8lu kB\n"
@@ -66,6 +73,9 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
mm->pinned_vm << (PAGE_SHIFT-10),
hiwater_rss << (PAGE_SHIFT-10),
total_rss << (PAGE_SHIFT-10),
+ anon << (PAGE_SHIFT-10),
+ file << (PAGE_SHIFT-10),
+ shmem << (PAGE_SHIFT-10),
data << (PAGE_SHIFT-10),
mm->stack_vm << (PAGE_SHIFT-10), text, lib,
ptes >> 10,

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