linux/Documentation/filesystems
Rik van Riel 34e431b0ae /proc/meminfo: provide estimated available memory
Many load balancing and workload placing programs check /proc/meminfo to
estimate how much free memory is available.  They generally do this by
adding up "free" and "cached", which was fine ten years ago, but is
pretty much guaranteed to be wrong today.

It is wrong because Cached includes memory that is not freeable as page
cache, for example shared memory segments, tmpfs, and ramfs, and it does
not include reclaimable slab memory, which can take up a large fraction
of system memory on mostly idle systems with lots of files.

Currently, the amount of memory that is available for a new workload,
without pushing the system into swap, can be estimated from MemFree,
Active(file), Inactive(file), and SReclaimable, as well as the "low"
watermarks from /proc/zoneinfo.

However, this may change in the future, and user space really should not
be expected to know kernel internals to come up with an estimate for the
amount of free memory.

It is more convenient to provide such an estimate in /proc/meminfo.  If
things change in the future, we only have to change it in one place.

Signed-off-by: Rik van Riel <riel@redhat.com>
Reported-by: Erik Mouw <erik.mouw_2@nxp.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-21 16:19:43 -08:00
..
caching FS-Cache: Provide the ability to enable/disable cookies 2013-09-27 18:40:25 +01:00
cifs cifs: update cifs.txt and remove some outdated infos 2013-09-13 16:29:58 -05:00
configfs configfs: convert to umode_t 2012-01-03 22:54:57 -05:00
nfs doc: filesystems : Fix typo in Documentations/filesystems 2013-08-20 13:45:56 +02:00
pohmelfs Documentation: Fix multiple typo in Documentation 2012-03-07 16:08:24 +01:00
9p.txt 9p: fix 9p.txt to advertise msize instead of maxdata 2011-10-24 11:13:12 -05:00
00-INDEX Introduce a new file system, Flash-Friendly File System (F2FS), to Linux 3.8. 2012-12-20 13:54:52 -08:00
adfs.txt
affs.txt
afs.txt
autofs4-mount-control.txt
automount-support.txt
befs.txt Documentation: befs.txt: no maintainer, orphaned 2011-08-13 18:34:03 -07:00
bfs.txt
btrfs.txt Documentation: filesystems: update btrfs tools section 2013-11-21 11:51:50 -05:00
ceph.txt ceph: enable/disable dentry complete flags via mount option 2012-01-12 11:00:40 -08:00
coda.txt
cramfs.txt
debugfs.txt debugfs: more tightly restrict default mount mode 2012-08-27 13:42:02 -07:00
devpts.txt
directory-locking vfs: take i_mutex on renamed file 2013-11-09 00:16:40 -05:00
dlmfs.txt
dnotify_test.c
dnotify.txt
ecryptfs.txt
efivarfs.txt efivarfs: Add documentation for the EFI variable filesystem 2012-10-30 10:39:18 +00:00
exofs.txt
ext2.txt
ext3.txt ext3: allow specifying external journal by pathname mount option 2013-07-31 22:11:15 +02:00
ext4.txt Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-09-06 09:36:28 -07:00
f2fs.txt f2fs: update f2fs document 2013-11-01 11:20:05 +09:00
fiemap.txt
files.txt Wrap accesses to the fd_sets in struct fdtable 2012-02-19 10:30:52 -08:00
fuse.txt
gfs2-glocks.txt GFS2: Update glock doc to add new stats info 2012-05-10 12:41:40 +01:00
gfs2-uevents.txt Documentation: Fix multiple typo in Documentation 2012-03-07 16:08:24 +01:00
gfs2.txt GFS2: Update main gfs2 doc 2012-05-10 11:45:31 +01:00
hfs.txt Documentation: HFS is orphaned 2011-11-04 12:01:48 -07:00
hfsplus.txt
hpfs.txt
inotify.txt Documentation: fix inotify source file paths 2011-11-04 12:01:47 -07:00
isofs.txt
jfs.txt doc: fix misspellings with 'codespell' tool 2013-05-28 12:02:12 +02:00
Locking Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-07-03 09:10:19 -07:00
locks.txt doc: fix broken references 2011-09-27 18:08:04 +02:00
logfs.txt
Makefile
mandatory-locking.txt
ncpfs.txt
nilfs2.txt
ntfs.txt
ocfs2.txt
omfs.txt
path-lookup.txt
porting iget/iget5: don't bother with ->i_lock until we find a match 2013-11-09 00:16:31 -05:00
proc.txt /proc/meminfo: provide estimated available memory 2014-01-21 16:19:43 -08:00
qnx6.txt doc: filesystems : Fix typo in Documentations/filesystems 2013-08-20 13:45:56 +02:00
quota.txt
ramfs-rootfs-initramfs.txt initmpfs: use initramfs if rootfstype= or root= specified 2013-09-11 15:59:38 -07:00
relay.txt doc: Fix typo in doucmentations 2013-07-25 12:34:15 +02:00
romfs.txt
seq_file.txt
sharedsubtree.txt
spufs.txt
squashfs.txt Squashfs: Update documentation to include xattrs 2011-12-30 01:20:24 +00:00
sysfs-pci.txt
sysfs-tagging.txt doc: Fix typo in doucmentations 2013-07-25 12:34:15 +02:00
sysfs.txt sysfs: propagate umode_t 2012-01-03 22:55:03 -05:00
sysv-fs.txt
tmpfs.txt
ubifs.txt
udf.txt
ufs.txt
vfat.txt Documentation/filesystems/vfat.txt: fix directory entry example 2013-11-13 12:09:32 +09:00
vfs.txt vfs: improve i_op->atomic_open() documentation 2013-09-16 19:17:24 -04:00
xfs-delayed-logging-design.txt
xfs-self-describing-metadata.txt xfs: add metadata CRC documentation 2013-04-27 13:27:43 -05:00
xfs.txt doc: filesystems : Fix typo in Documentations/filesystems 2013-08-20 13:45:56 +02:00
xip.txt