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Commit 0bc126d4 authored by Rodrigo Freire's avatar Rodrigo Freire Committed by Linus Torvalds
Browse files

Documentation/filesystems: describe the shared memory usage/accounting 



The Shared Memory accounting support is present in Kernel since commit
4b02108a ("mm: oom analysis: add shmem vmstat") and in userland
free(1) since 2014.  This patch updates the Documentation to reflect
this change.

Signed-off-by: default avatarRodrigo Freire <rfreire@redhat.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6f754ba4

Documentation/filesystems/proc.txt

+2 −0
Original line number Diff line number Diff line
@@ -855,6 +855,7 @@ Dirty: 968 kB 
Writeback:           0 kB

AnonPages:      861800 kB

Mapped:         280372 kB

Shmem:             644 kB

Slab:           284364 kB

SReclaimable:   159856 kB

SUnreclaim:     124508 kB
@@ -911,6 +912,7 @@ MemAvailable: An estimate of how much memory is available for starting new 
   AnonPages: Non-file backed pages mapped into userspace page tables

AnonHugePages: Non-file backed huge pages mapped into userspace page tables

      Mapped: files which have been mmaped, such as libraries

       Shmem: Total memory used by shared memory (shmem) and tmpfs

        Slab: in-kernel data structures cache

SReclaimable: Part of Slab, that might be reclaimed, such as caches

  SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure

Documentation/filesystems/tmpfs.txt

+4 −4
Original line number Diff line number Diff line
@@ -17,10 +17,10 @@ RAM, where you have to create an ordinary filesystem on top. Ramdisks 
cannot swap and you do not have the possibility to resize them. 



Since tmpfs lives completely in the page cache and on swap, all tmpfs

pages currently in memory will show up as cached. It will not show up

as shared or something like that. Further on you can check the actual

RAM+swap use of a tmpfs instance with df(1) and du(1).



pages will be shown as "Shmem" in /proc/meminfo and "Shared" in

free(1). Notice that these counters also include shared memory

(shmem, see ipcs(1)). The most reliable way to get the count is

using df(1) and du(1).



tmpfs has the following uses: