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authorAndrew Morton <akpm@osdl.org>2006-01-08 04:00:39 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-08 23:12:40 -0500
commit9d0243bca345d5ce25d3f4b74b7facb3a6df1232 (patch)
treea3a0a763bf83a483282dc1c3caab587941a98fc2 /Documentation/filesystems/proc.txt
parentbec6b0c89b234090681a4516e20ac5debe3e7c59 (diff)
[PATCH] drop-pagecache
Add /proc/sys/vm/drop_caches. When written to, this will cause the kernel to discard as much pagecache and/or reclaimable slab objects as it can. THis operation requires root permissions. It won't drop dirty data, so the user should run `sync' first. Caveats: a) Holds inode_lock for exorbitant amounts of time. b) Needs to be taught about NUMA nodes: propagate these all the way through so the discarding can be controlled on a per-node basis. This is a debugging feature: useful for getting consistent results between filesystem benchmarks. We could possibly put it under a config option, but it's less than 300 bytes. Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation/filesystems/proc.txt')
-rw-r--r--Documentation/filesystems/proc.txt17
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index d4773565ea2f..a4dcf42c2fd9 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1302,6 +1302,23 @@ VM has token based thrashing control mechanism and uses the token to prevent
1302unnecessary page faults in thrashing situation. The unit of the value is 1302unnecessary page faults in thrashing situation. The unit of the value is
1303second. The value would be useful to tune thrashing behavior. 1303second. The value would be useful to tune thrashing behavior.
1304 1304
1305drop_caches
1306-----------
1307
1308Writing to this will cause the kernel to drop clean caches, dentries and
1309inodes from memory, causing that memory to become free.
1310
1311To free pagecache:
1312 echo 1 > /proc/sys/vm/drop_caches
1313To free dentries and inodes:
1314 echo 2 > /proc/sys/vm/drop_caches
1315To free pagecache, dentries and inodes:
1316 echo 3 > /proc/sys/vm/drop_caches
1317
1318As this is a non-destructive operation and dirty objects are not freeable, the
1319user should run `sync' first.
1320
1321
13052.5 /proc/sys/dev - Device specific parameters 13222.5 /proc/sys/dev - Device specific parameters
1306---------------------------------------------- 1323----------------------------------------------
1307 1324