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--- proc:smaps_file [2017/04/05 09:58] – peter
+++ proc:smaps_file [2020/07/15 09:30] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 ====== 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.
@@ Line 5: / Line 7: @@
 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.
-The **/proc/PID/smaps** is an extension based on maps, showing the memory consumption for each of the process's mappings.  For each of mappings there is a series of lines such as the following:
+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|
@@ Line 22: / Line 29: @@
 |MMUPageSize:|4 kB|
-The first of these lines shows the same information as is displayed for the
+where:
-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
+  * **Size** is the size of the mapping.
-process' proportional share of this mapping (PSS), the number of clean and
+  * **RSS** is the amount of the mapping that is currently resident in RAM.
-dirty private pages in the mapping.  Note that even a page which is part of a
+  * **PSS** is the process' proportional share of this mapping.
-MAP_SHARED mapping, but has only a single pte mapped, i.e.  is currently used
+  * **Shared_Clean** is the number of clean shared pages in the mapping.
-by only one process, is accounted as private and not as shared.  "Referenced"
+  * **Shared_Dirty** is the number of dirty shared pages in the mapping.
-indicates the amount of memory currently marked as referenced or accessed.
+  * **Private_Clean** is the number of clean private pages in the mapping.
-"Anonymous" shows the amount of memory that does not belong to any file.  Even
+  * **Private_Dirty** is the number of dirty private pages in the mapping.
-a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
+  * **Referenced** indicates the amount of memory currently marked as referenced or accessed.
-and a page is modified, the file page is replaced by a private anonymous copy.
+  * **Anonymous** shows the amount of memory that does not belong to any file.
-"Swap" shows how much would-be-anonymous memory is also used, but out on
+    * 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.
+  * **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.
-This file is only present if the CONFIG_MMU kernel configuration option is
-enabled.