[IPV4]: Optimize inet_getpeer()
1) Some sysctl vars are declared __read_mostly
2) We can avoid updating stack[] when doing an AVL lookup only.
lookup() macro is extended to receive a second parameter, that may be NULL
in case of a pure lookup (no need to save the AVL path). This removes
unnecessary instructions, because compiler knows if this _stack parameter is
NULL or not.
text size of net/ipv4/inetpeer.o is 2063 bytes instead of 2107 on x86_64
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index db3ef96..2f44e61 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -87,10 +87,12 @@
static int peer_total;
/* Exported for sysctl_net_ipv4. */
-int inet_peer_threshold = 65536 + 128; /* start to throw entries more
+int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries more
* aggressively at this stage */
-int inet_peer_minttl = 120 * HZ; /* TTL under high load: 120 sec */
-int inet_peer_maxttl = 10 * 60 * HZ; /* usual time to live: 10 min */
+int inet_peer_minttl __read_mostly = 120 * HZ; /* TTL under high load: 120 sec */
+int inet_peer_maxttl __read_mostly = 10 * 60 * HZ; /* usual time to live: 10 min */
+int inet_peer_gc_mintime __read_mostly = 10 * HZ;
+int inet_peer_gc_maxtime __read_mostly = 120 * HZ;
static struct inet_peer *inet_peer_unused_head;
static struct inet_peer **inet_peer_unused_tailp = &inet_peer_unused_head;
@@ -99,9 +101,6 @@
static void peer_check_expire(unsigned long dummy);
static DEFINE_TIMER(peer_periodic_timer, peer_check_expire, 0, 0);
-/* Exported for sysctl_net_ipv4. */
-int inet_peer_gc_mintime = 10 * HZ,
- inet_peer_gc_maxtime = 120 * HZ;
/* Called from ip_output.c:ip_init */
void __init inet_initpeers(void)
@@ -151,20 +150,27 @@
spin_unlock_bh(&inet_peer_unused_lock);
}
-/* Called with local BH disabled and the pool lock held. */
-#define lookup(daddr) \
+/*
+ * Called with local BH disabled and the pool lock held.
+ * _stack is known to be NULL or not at compile time,
+ * so compiler will optimize the if (_stack) tests.
+ */
+#define lookup(_daddr,_stack) \
({ \
struct inet_peer *u, **v; \
- stackptr = stack; \
- *stackptr++ = &peer_root; \
+ if (_stack) { \
+ stackptr = _stack; \
+ *stackptr++ = &peer_root; \
+ } \
for (u = peer_root; u != peer_avl_empty; ) { \
- if (daddr == u->v4daddr) \
+ if (_daddr == u->v4daddr) \
break; \
- if ((__force __u32)daddr < (__force __u32)u->v4daddr) \
+ if ((__force __u32)_daddr < (__force __u32)u->v4daddr) \
v = &u->avl_left; \
else \
v = &u->avl_right; \
- *stackptr++ = v; \
+ if (_stack) \
+ *stackptr++ = v; \
u = *v; \
} \
u; \
@@ -288,7 +294,7 @@
if (atomic_read(&p->refcnt) == 1) {
struct inet_peer **stack[PEER_MAXDEPTH];
struct inet_peer ***stackptr, ***delp;
- if (lookup(p->v4daddr) != p)
+ if (lookup(p->v4daddr, stack) != p)
BUG();
delp = stackptr - 1; /* *delp[0] == p */
if (p->avl_left == peer_avl_empty) {
@@ -373,7 +379,7 @@
/* Look up for the address quickly. */
read_lock_bh(&peer_pool_lock);
- p = lookup(daddr);
+ p = lookup(daddr, NULL);
if (p != peer_avl_empty)
atomic_inc(&p->refcnt);
read_unlock_bh(&peer_pool_lock);
@@ -400,7 +406,7 @@
write_lock_bh(&peer_pool_lock);
/* Check if an entry has suddenly appeared. */
- p = lookup(daddr);
+ p = lookup(daddr, stack);
if (p != peer_avl_empty)
goto out_free;
