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[PATCH] drop-pagecache

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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>
This commit is contained in:
Andrew Morton 2006-01-08 01:00:39 -08:00 • committed by Linus Torvalds
parent bec6b0c89b
commit 9d0243bca3
9 changed files with 107 additions and 5 deletions
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10
kernel/sysctl.c
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@ -68,6 +68,7 @@ extern int min_free_kbytes;
extern int printk_ratelimit_jiffies;
extern int printk_ratelimit_burst;
extern int pid_max_min, pid_max_max;
extern int sysctl_drop_caches;
#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
int unknown_nmi_panic;
@ -774,6 +775,15 @@ static ctl_table vm_table[] = {
.proc_handler = &lowmem_reserve_ratio_sysctl_handler,
.strategy = &sysctl_intvec,
},
{
.ctl_name = VM_DROP_PAGECACHE,
.procname = "drop_caches",
.data = &sysctl_drop_caches,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = drop_caches_sysctl_handler,
.strategy = &sysctl_intvec,
},
{
.ctl_name = VM_MIN_FREE_KBYTES,
.procname = "min_free_kbytes",