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[PATCH] dcache: avoid RCU for never-hashed dentries

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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 <dada1@cosmosbay.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Maneesh Soni <maneesh@in.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Acked-by: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Eric Dumazet 2006-12-06 20:38:48 -08:00 • committed by Linus Torvalds
parent d18de5a272
commit b3423415fb
1 changed files with 12 additions and 4 deletions
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16
fs/dcache.c
View file

@ -68,15 +68,19 @@ struct dentry_stat_t dentry_stat = {
.age_limit = 45, .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)) if (dname_external(dentry))
kfree(dentry->d_name.name); kfree(dentry->d_name.name);
kmem_cache_free(dentry_cache, dentry); 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 * no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
* inside dcache_lock. * inside dcache_lock.
@ -85,7 +89,11 @@ static void d_free(struct dentry *dentry)
{ {
if (dentry->d_op && dentry->d_op->d_release) if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry); 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);
} }
/* /*