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authorDave Hansen <dave@linux.vnet.ibm.com>2014-04-03 14:48:19 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-03 16:21:04 -0700
commit5509a5d27b971a90b940e148ca9ca53312e4fa7a (patch)
treea05845240563a79deafc3350e6409c6b3058e0f2 /kernel
parent67f9fd91f93c582b7de2ab9325b6e179db77e4d5 (diff)
downloadlinux-5509a5d27b971a90b940e148ca9ca53312e4fa7a.tar.gz
drop_caches: add some documentation and info message
There is plenty of anecdotal evidence and a load of blog posts suggesting that using "drop_caches" periodically keeps your system running in "tip top shape". Perhaps adding some kernel documentation will increase the amount of accurate data on its use. If we are not shrinking caches effectively, then we have real bugs. Using drop_caches will simply mask the bugs and make them harder to find, but certainly does not fix them, nor is it an appropriate "workaround" to limit the size of the caches. On the contrary, there have been bug reports on issues that turned out to be misguided use of cache dropping. Dropping caches is a very drastic and disruptive operation that is good for debugging and running tests, but if it creates bug reports from production use, kernel developers should be aware of its use. Add a bit more documentation about it, a syslog message to track down abusers, and vmstat drop counters to help analyze problem reports. [akpm@linux-foundation.org: checkpatch fixes] [hannes@cmpxchg.org: add runtime suppression control] Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com> Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sysctl.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 09d2e241360..5c14b547882 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -123,7 +123,7 @@ static int __maybe_unused neg_one = -1;
static int zero;
static int __maybe_unused one = 1;
static int __maybe_unused two = 2;
-static int __maybe_unused three = 3;
+static int __maybe_unused four = 4;
static unsigned long one_ul = 1;
static int one_hundred = 100;
#ifdef CONFIG_PRINTK
@@ -1264,7 +1264,7 @@ static struct ctl_table vm_table[] = {
.mode = 0644,
.proc_handler = drop_caches_sysctl_handler,
.extra1 = &one,
- .extra2 = &three,
+ .extra2 = &four,
},
#ifdef CONFIG_COMPACTION
{