From 9d0243bca345d5ce25d3f4b74b7facb3a6df1232 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Sun, 8 Jan 2006 01:00:39 -0800 Subject: [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 Signed-off-by: Linus Torvalds --- fs/drop_caches.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) create mode 100644 fs/drop_caches.c (limited to 'fs/drop_caches.c') diff --git a/fs/drop_caches.c b/fs/drop_caches.c new file mode 100644 index 000000000000..4e4762389bdc --- /dev/null +++ b/fs/drop_caches.c @@ -0,0 +1,68 @@ +/* + * Implement the manual drop-all-pagecache function + */ + +#include +#include +#include +#include +#include +#include + +/* 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; +} -- cgit