[patch 10/35] fs: icache atomic inodes_stat
From: npiggin
Date: Mon Oct 18 2010 - 23:56:30 EST
Protect inodes_stat statistics with atomic ops rather than inode_lock.
Also move nr_inodes statistic into low level inode init and teardown
functions in anticipation of future patches which skip putting some
inodes (eg. sockets) onto sb list.
Signed-off-by: Nick Piggin <npiggin@xxxxxxxxx>
---
fs/fs-writeback.c | 6 ++++--
fs/inode.c | 28 +++++++++++++---------------
include/linux/fs.h | 11 ++++++++---
3 files changed, 25 insertions(+), 20 deletions(-)
Index: linux-2.6/fs/fs-writeback.c
===================================================================
--- linux-2.6.orig/fs/fs-writeback.c 2010-10-19 14:37:09.000000000 +1100
+++ linux-2.6/fs/fs-writeback.c 2010-10-19 14:37:31.000000000 +1100
@@ -772,7 +772,8 @@
wb->last_old_flush = jiffies;
nr_pages = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS) +
- (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+ (atomic_read(&inodes_stat.nr_inodes) -
+ atomic_read(&inodes_stat.nr_unused));
if (nr_pages) {
struct wb_writeback_work work = {
@@ -1156,7 +1157,8 @@
WARN_ON(!rwsem_is_locked(&sb->s_umount));
work.nr_pages = nr_dirty + nr_unstable +
- (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+ (atomic_read(&inodes_stat.nr_inodes) -
+ atomic_read(&inodes_stat.nr_unused));
bdi_queue_work(sb->s_bdi, &work);
wait_for_completion(&done);
Index: linux-2.6/fs/inode.c
===================================================================
--- linux-2.6.orig/fs/inode.c 2010-10-19 14:37:09.000000000 +1100
+++ linux-2.6/fs/inode.c 2010-10-19 14:37:56.000000000 +1100
@@ -122,7 +122,10 @@
/*
* Statistics gathering..
*/
-struct inodes_stat_t inodes_stat;
+struct inodes_stat_t inodes_stat = {
+ .nr_inodes = ATOMIC_INIT(0),
+ .nr_unused = ATOMIC_INIT(0),
+};
static struct kmem_cache *inode_cachep __read_mostly;
@@ -213,6 +216,8 @@
inode->i_fsnotify_mask = 0;
#endif
+ atomic_inc(&inodes_stat.nr_inodes);
+
return 0;
out:
return -ENOMEM;
@@ -253,6 +258,7 @@
if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
posix_acl_release(inode->i_default_acl);
#endif
+ atomic_dec(&inodes_stat.nr_inodes);
}
EXPORT_SYMBOL(__destroy_inode);
@@ -313,7 +319,7 @@
list_move(&inode->i_list, &inode_in_use);
spin_unlock(&wb_inode_list_lock);
}
- inodes_stat.nr_unused--;
+ atomic_dec(&inodes_stat.nr_unused);
}
void end_writeback(struct inode *inode)
@@ -354,8 +360,6 @@
*/
static void dispose_list(struct list_head *head)
{
- int nr_disposed = 0;
-
while (!list_empty(head)) {
struct inode *inode;
@@ -375,11 +379,7 @@
wake_up_inode(inode);
destroy_inode(inode);
- nr_disposed++;
}
- spin_lock(&inode_lock);
- inodes_stat.nr_inodes -= nr_disposed;
- spin_unlock(&inode_lock);
}
/*
@@ -428,7 +428,7 @@
busy = 1;
}
/* only unused inodes may be cached with i_count zero */
- inodes_stat.nr_unused -= count;
+ atomic_sub(count, &inodes_stat.nr_unused);
return busy;
}
@@ -545,7 +545,7 @@
spin_unlock(&inode->i_lock);
nr_pruned++;
}
- inodes_stat.nr_unused -= nr_pruned;
+ atomic_sub(nr_pruned, &inodes_stat.nr_unused);
if (current_is_kswapd())
__count_vm_events(KSWAPD_INODESTEAL, reap);
else
@@ -574,7 +574,7 @@
unsigned long nr;
shrinker_add_scan(&nr_to_scan, scanned, global,
- inodes_stat.nr_unused,
+ atomic_read(&inodes_stat.nr_unused),
SHRINK_DEFAULT_SEEKS * 100 / sysctl_vfs_cache_pressure);
/*
* Nasty deadlock avoidance. We may hold various FS locks,
@@ -680,7 +680,6 @@
__inode_add_to_lists(struct super_block *sb, struct hlist_head *head,
struct inode *inode)
{
- inodes_stat.nr_inodes++;
spin_lock(&sb_inode_list_lock);
list_add(&inode->i_sb_list, &sb->s_inodes);
spin_unlock(&sb_inode_list_lock);
@@ -1344,7 +1343,7 @@
list_move(&inode->i_list, &inode_unused);
spin_unlock(&wb_inode_list_lock);
}
- inodes_stat.nr_unused++;
+ atomic_inc(&inodes_stat.nr_unused);
if (sb->s_flags & MS_ACTIVE) {
spin_unlock(&inode->i_lock);
spin_unlock(&sb_inode_list_lock);
@@ -1362,10 +1361,10 @@
spin_lock(&inode->i_lock);
WARN_ON(inode->i_state & I_NEW);
inode->i_state &= ~I_WILL_FREE;
- inodes_stat.nr_unused--;
spin_lock(&inode_hash_lock);
hlist_del_init(&inode->i_hash);
spin_unlock(&inode_hash_lock);
+ atomic_dec(&inodes_stat.nr_unused);
}
spin_lock(&wb_inode_list_lock);
list_del_init(&inode->i_list);
@@ -1374,7 +1373,6 @@
spin_unlock(&sb_inode_list_lock);
WARN_ON(inode->i_state & I_NEW);
inode->i_state |= I_FREEING;
- inodes_stat.nr_inodes--;
spin_unlock(&inode->i_lock);
spin_unlock(&inode_lock);
evict(inode);
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h 2010-10-19 14:37:09.000000000 +1100
+++ linux-2.6/include/linux/fs.h 2010-10-19 14:37:31.000000000 +1100
@@ -40,12 +40,17 @@
};
struct inodes_stat_t {
- int nr_inodes;
- int nr_unused;
+ /*
+ * Using atomics here is a hack which should just happen to
+ * work on all architectures today. Not a big deal though,
+ * because it goes away and gets fixed properly later in the
+ * inode scaling series.
+ */
+ atomic_t nr_inodes;
+ atomic_t nr_unused;
int dummy[5]; /* padding for sysctl ABI compatibility */
};
-
#define NR_FILE 8192 /* this can well be larger on a larger system */
#define MAY_EXEC 1
--
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