From: Eric Dumazet Date: Thu, 7 Dec 2006 04:38:48 +0000 (-0800) Subject: [PATCH] dcache: avoid RCU for never-hashed dentries X-Git-Tag: v2.6.20-rc1~145^2^2~111 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b3423415fbc2e5461605826317da1c8dbbf21f97;p=linux-2.6 [PATCH] dcache: avoid RCU for never-hashed dentries Some dentries don't need to be globally visible in dentry hashtable. (pipes & sockets) Such dentries dont need to wait for a RCU grace period at delete time. Being able to free them permits a better CPU cache use (hot cache) This patch combined with (dont insert pipe dentries into dentry_hashtable) reduced time of { pipe(p); close(p[0]); close(p[1]);} on my UP machine (1.6 GHz Pentium-M) from 3.23 us to 2.86 us (But this patch does not depend on other patches, only bench results) Signed-off-by: Eric Dumazet Cc: Al Viro Cc: Maneesh Soni Cc: "Paul E. McKenney" Cc: Dipankar Sarma Acked-by: David Miller Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/dcache.c b/fs/dcache.c index a7c67cee5d..d68631f18d 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -68,15 +68,19 @@ struct dentry_stat_t dentry_stat = { .age_limit = 45, }; -static void d_callback(struct rcu_head *head) +static void __d_free(struct dentry *dentry) { - struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu); - if (dname_external(dentry)) kfree(dentry->d_name.name); kmem_cache_free(dentry_cache, dentry); } +static void d_callback(struct rcu_head *head) +{ + struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu); + __d_free(dentry); +} + /* * no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry * inside dcache_lock. @@ -85,7 +89,11 @@ static void d_free(struct dentry *dentry) { if (dentry->d_op && dentry->d_op->d_release) dentry->d_op->d_release(dentry); - call_rcu(&dentry->d_u.d_rcu, d_callback); + /* if dentry was never inserted into hash, immediate free is OK */ + if (dentry->d_hash.pprev == NULL) + __d_free(dentry); + else + call_rcu(&dentry->d_u.d_rcu, d_callback); } /*