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authorAndrew Morton <akpm@osdl.org>2006-01-08 01:00:39 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-08 20:12:40 -0800
commit9d0243bca345d5ce25d3f4b74b7facb3a6df1232 (patch)
treea3a0a763bf83a483282dc1c3caab587941a98fc2 /fs/drop_caches.c
parentbec6b0c89b234090681a4516e20ac5debe3e7c59 (diff)
downloadlinux-9d0243bca345d5ce25d3f4b74b7facb3a6df1232.tar.gz
[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 'fs/drop_caches.c')
-rw-r--r--fs/drop_caches.c68
1 files changed, 68 insertions, 0 deletions
diff --git a/fs/drop_caches.c b/fs/drop_caches.c
new file mode 100644
index 00000000000..4e4762389bd
--- /dev/null
+++ b/fs/drop_caches.c
@@ -0,0 +1,68 @@
+/*
+ * Implement the manual drop-all-pagecache function
+ */
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/writeback.h>
+#include <linux/sysctl.h>
+#include <linux/gfp.h>
+
+/* A global variable is a bit ugly, but it keeps the code simple */
+int sysctl_drop_caches;
+
+static void drop_pagecache_sb(struct super_block *sb)
+{
+ struct inode *inode;
+
+ spin_lock(&inode_lock);
+ list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ if (inode->i_state & (I_FREEING|I_WILL_FREE))
+ continue;
+ invalidate_inode_pages(inode->i_mapping);
+ }
+ spin_unlock(&inode_lock);
+}
+
+void drop_pagecache(void)
+{
+ struct super_block *sb;
+
+ spin_lock(&sb_lock);
+restart:
+ list_for_each_entry(sb, &super_blocks, s_list) {
+ sb->s_count++;
+ spin_unlock(&sb_lock);
+ down_read(&sb->s_umount);
+ if (sb->s_root)
+ drop_pagecache_sb(sb);
+ up_read(&sb->s_umount);
+ spin_lock(&sb_lock);
+ if (__put_super_and_need_restart(sb))
+ goto restart;
+ }
+ spin_unlock(&sb_lock);
+}
+
+void drop_slab(void)
+{
+ int nr_objects;
+
+ do {
+ nr_objects = shrink_slab(1000, GFP_KERNEL, 1000);
+ } while (nr_objects > 10);
+}
+
+int drop_caches_sysctl_handler(ctl_table *table, int write,
+ struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
+{
+ proc_dointvec_minmax(table, write, file, buffer, length, ppos);
+ if (write) {
+ if (sysctl_drop_caches & 1)
+ drop_pagecache();
+ if (sysctl_drop_caches & 2)
+ drop_slab();
+ }
+ return 0;
+}