[patch 23/52] fs: dcache percpu nr_dentry

[npiggin]

The nr_dentry stat is a globally touched cacheline and atomic operation
twice over the lifetime of a dentry. It is used for the benfit of userspace
only. We could make a per-cpu counter or something for it, but it is only
accessed via proc, so we could use slab stats.

XXX: must implement slab routines to return stats for a single cache, and
implement the proc handler.

Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
---
 fs/dcache.c            |    5 +----
 include/linux/dcache.h |    2 +-
 2 files changed, 2 insertions(+), 5 deletions(-)

Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c
+++ linux-2.6/fs/dcache.c
@@ -105,7 +105,7 @@ static struct dcache_hash_bucket *dentry
 
 /* Statistics gathering. */
 struct dentry_stat_t dentry_stat = {
-	.nr_dentry = ATOMIC_INIT(0),
+	.nr_dentry = 0,
 	.age_limit = 45,
 };
 
@@ -146,7 +146,6 @@ static void d_callback(struct rcu_head *
  */
 static void d_free(struct dentry *dentry)
 {
-	atomic_dec(&dentry_stat.nr_dentry);
 	BUG_ON(dentry->d_count);
 	if (dentry->d_op && dentry->d_op->d_release)
 		dentry->d_op->d_release(dentry);
@@ -1249,8 +1248,6 @@ struct dentry *d_alloc(struct dentry * p
 		spin_unlock(&parent->d_lock);
 	}
 
-	atomic_inc(&dentry_stat.nr_dentry);
-
 	return dentry;
 }
 EXPORT_SYMBOL(d_alloc);
Index: linux-2.6/include/linux/dcache.h
===================================================================
--- linux-2.6.orig/include/linux/dcache.h
+++ linux-2.6/include/linux/dcache.h
@@ -38,7 +38,7 @@ struct qstr {
 };
 
 struct dentry_stat_t {
-	atomic_t nr_dentry;
+	int nr_dentry;		/* unused */
 	int nr_unused;		/* protected by dcache_lru_lock */
 	int age_limit;          /* age in seconds */
 	int want_pages;         /* pages requested by system */


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