====== Proc - smaps file ======

The **/proc/PID/smaps** is an extension based on maps, showing the memory consumption for each of the process's mappings.  This file is only present if the **CONFIG_MMU** kernel configuration option is enabled.

For SMP CONFIG users.

For making accounting scalable, RSS related information are handled in asynchronous manner and the value may not be very precise.  To see a precise snapshot of a moment, you can see **/proc/<pid>/smaps** file and scan page table.  It's slow but very precise.

For each of mappings there is a series of lines such as the following:

^address^perms^offset^dev^inode^pathname^
|08048000-080bc000|r-xp|00000000|03:02|13130|/bin/bash|

This shows the same information as is displayed for the mapping in [[Proc:maps file|/proc/PID/maps]].

Additional information is also shown:

|Size:|1084 kB|
|Rss:|892 kB|
|Pss:|374 kB|
|Shared_Clean:|892 kB|
|Shared_Dirty:|0 kB|
|Private_Clean:|0 kB|
|Private_Dirty:|0 kB|
|Referenced:|892 kB|
|Anonymous:|0 kB|
|Swap:|0 kB|
|KernelPageSize:|4 kB|
|MMUPageSize:|4 kB|

where:

  * **Size** is the size of the mapping.
  * **RSS** is the amount of the mapping that is currently resident in RAM.
  * **PSS** is the process' proportional share of this mapping.
  * **Shared_Clean** is the number of clean shared pages in the mapping.
  * **Shared_Dirty** is the number of dirty shared pages in the mapping.
  * **Private_Clean** is the number of clean private pages in the mapping.
  * **Private_Dirty** is the number of dirty private pages in the mapping.
  * **Referenced** indicates the amount of memory currently marked as referenced or accessed.
  * **Anonymous** shows the amount of memory that does not belong to any file.
    * Even a mapping associated with a file may contain anonymous pages: when **MAP_PRIVATE** 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 swap.
  
**NOTE:**  Even a page which is part of a **MAP_SHARED** mapping, but which only has a single private mapped, i.e. is currently used by only one process, is accounted as __private__ and not as shared.