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/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.