[AF_UNIX]: Convert to use a spinlock instead of rwlock
From: Benjamin LaHaise <bcrl@kvack.org>
In af_unix, a rwlock is used to protect internal state. At least on my
P4 with HT it is faster to use a spinlock due to the simpler memory
barrier used to unlock. This patch raises bw_unix to ~690K/s.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 3f302ae..bfc1779 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -58,10 +58,10 @@
#define UNIXCB(skb) (*(struct unix_skb_parms*)&((skb)->cb))
#define UNIXCREDS(skb) (&UNIXCB((skb)).creds)
-#define unix_state_rlock(s) read_lock(&unix_sk(s)->lock)
-#define unix_state_runlock(s) read_unlock(&unix_sk(s)->lock)
-#define unix_state_wlock(s) write_lock(&unix_sk(s)->lock)
-#define unix_state_wunlock(s) write_unlock(&unix_sk(s)->lock)
+#define unix_state_rlock(s) spin_lock(&unix_sk(s)->lock)
+#define unix_state_runlock(s) spin_unlock(&unix_sk(s)->lock)
+#define unix_state_wlock(s) spin_lock(&unix_sk(s)->lock)
+#define unix_state_wunlock(s) spin_unlock(&unix_sk(s)->lock)
#ifdef __KERNEL__
/* The AF_UNIX socket */
@@ -76,7 +76,7 @@
struct sock *other;
struct sock *gc_tree;
atomic_t inflight;
- rwlock_t lock;
+ spinlock_t lock;
wait_queue_head_t peer_wait;
};
#define unix_sk(__sk) ((struct unix_sock *)__sk)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 7d3fe6a..1ddd36d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -564,7 +564,7 @@
u = unix_sk(sk);
u->dentry = NULL;
u->mnt = NULL;
- rwlock_init(&u->lock);
+ spin_lock_init(&u->lock);
atomic_set(&u->inflight, sock ? 0 : -1);
init_MUTEX(&u->readsem); /* single task reading lock */
init_waitqueue_head(&u->peer_wait);