[NET]: Hashed spinlocks in net/ipv4/route.c
- Locking abstraction
- Spinlocks moved out of rt hash table : Less memory (50%) used by rt
hash table. it's a win even on UP.
- Sizing of spinlocks table depends on NR_CPUS
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 12a1cf3..daf82f8 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -54,6 +54,7 @@
* Marc Boucher : routing by fwmark
* Robert Olsson : Added rt_cache statistics
* Arnaldo C. Melo : Convert proc stuff to seq_file
+ * Eric Dumazet : hashed spinlocks
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@@ -201,8 +202,37 @@
struct rt_hash_bucket {
struct rtable *chain;
- spinlock_t lock;
-} __attribute__((__aligned__(8)));
+};
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+/*
+ * Instead of using one spinlock for each rt_hash_bucket, we use a table of spinlocks
+ * The size of this table is a power of two and depends on the number of CPUS.
+ */
+#if NR_CPUS >= 32
+#define RT_HASH_LOCK_SZ 4096
+#elif NR_CPUS >= 16
+#define RT_HASH_LOCK_SZ 2048
+#elif NR_CPUS >= 8
+#define RT_HASH_LOCK_SZ 1024
+#elif NR_CPUS >= 4
+#define RT_HASH_LOCK_SZ 512
+#else
+#define RT_HASH_LOCK_SZ 256
+#endif
+
+static spinlock_t *rt_hash_locks;
+# define rt_hash_lock_addr(slot) &rt_hash_locks[(slot) & (RT_HASH_LOCK_SZ - 1)]
+# define rt_hash_lock_init() { \
+ int i; \
+ rt_hash_locks = kmalloc(sizeof(spinlock_t) * RT_HASH_LOCK_SZ, GFP_KERNEL); \
+ if (!rt_hash_locks) panic("IP: failed to allocate rt_hash_locks\n"); \
+ for (i = 0; i < RT_HASH_LOCK_SZ; i++) \
+ spin_lock_init(&rt_hash_locks[i]); \
+ }
+#else
+# define rt_hash_lock_addr(slot) NULL
+# define rt_hash_lock_init()
+#endif
static struct rt_hash_bucket *rt_hash_table;
static unsigned rt_hash_mask;
@@ -587,7 +617,7 @@
i = (i + 1) & rt_hash_mask;
rthp = &rt_hash_table[i].chain;
- spin_lock(&rt_hash_table[i].lock);
+ spin_lock(rt_hash_lock_addr(i));
while ((rth = *rthp) != NULL) {
if (rth->u.dst.expires) {
/* Entry is expired even if it is in use */
@@ -620,7 +650,7 @@
rt_free(rth);
#endif /* CONFIG_IP_ROUTE_MULTIPATH_CACHED */
}
- spin_unlock(&rt_hash_table[i].lock);
+ spin_unlock(rt_hash_lock_addr(i));
/* Fallback loop breaker. */
if (time_after(jiffies, now))
@@ -643,11 +673,11 @@
get_random_bytes(&rt_hash_rnd, 4);
for (i = rt_hash_mask; i >= 0; i--) {
- spin_lock_bh(&rt_hash_table[i].lock);
+ spin_lock_bh(rt_hash_lock_addr(i));
rth = rt_hash_table[i].chain;
if (rth)
rt_hash_table[i].chain = NULL;
- spin_unlock_bh(&rt_hash_table[i].lock);
+ spin_unlock_bh(rt_hash_lock_addr(i));
for (; rth; rth = next) {
next = rth->u.rt_next;
@@ -780,7 +810,7 @@
k = (k + 1) & rt_hash_mask;
rthp = &rt_hash_table[k].chain;
- spin_lock_bh(&rt_hash_table[k].lock);
+ spin_lock_bh(rt_hash_lock_addr(k));
while ((rth = *rthp) != NULL) {
if (!rt_may_expire(rth, tmo, expire)) {
tmo >>= 1;
@@ -812,7 +842,7 @@
goal--;
#endif /* CONFIG_IP_ROUTE_MULTIPATH_CACHED */
}
- spin_unlock_bh(&rt_hash_table[k].lock);
+ spin_unlock_bh(rt_hash_lock_addr(k));
if (goal <= 0)
break;
}
@@ -882,7 +912,7 @@
rthp = &rt_hash_table[hash].chain;
- spin_lock_bh(&rt_hash_table[hash].lock);
+ spin_lock_bh(rt_hash_lock_addr(hash));
while ((rth = *rthp) != NULL) {
#ifdef CONFIG_IP_ROUTE_MULTIPATH_CACHED
if (!(rth->u.dst.flags & DST_BALANCED) &&
@@ -908,7 +938,7 @@
rth->u.dst.__use++;
dst_hold(&rth->u.dst);
rth->u.dst.lastuse = now;
- spin_unlock_bh(&rt_hash_table[hash].lock);
+ spin_unlock_bh(rt_hash_lock_addr(hash));
rt_drop(rt);
*rp = rth;
@@ -949,7 +979,7 @@
if (rt->rt_type == RTN_UNICAST || rt->fl.iif == 0) {
int err = arp_bind_neighbour(&rt->u.dst);
if (err) {
- spin_unlock_bh(&rt_hash_table[hash].lock);
+ spin_unlock_bh(rt_hash_lock_addr(hash));
if (err != -ENOBUFS) {
rt_drop(rt);
@@ -990,7 +1020,7 @@
}
#endif
rt_hash_table[hash].chain = rt;
- spin_unlock_bh(&rt_hash_table[hash].lock);
+ spin_unlock_bh(rt_hash_lock_addr(hash));
*rp = rt;
return 0;
}
@@ -1058,7 +1088,7 @@
{
struct rtable **rthp;
- spin_lock_bh(&rt_hash_table[hash].lock);
+ spin_lock_bh(rt_hash_lock_addr(hash));
ip_rt_put(rt);
for (rthp = &rt_hash_table[hash].chain; *rthp;
rthp = &(*rthp)->u.rt_next)
@@ -1067,7 +1097,7 @@
rt_free(rt);
break;
}
- spin_unlock_bh(&rt_hash_table[hash].lock);
+ spin_unlock_bh(rt_hash_lock_addr(hash));
}
void ip_rt_redirect(u32 old_gw, u32 daddr, u32 new_gw,
@@ -3073,7 +3103,7 @@
int __init ip_rt_init(void)
{
- int i, order, goal, rc = 0;
+ int order, goal, rc = 0;
rt_hash_rnd = (int) ((num_physpages ^ (num_physpages>>8)) ^
(jiffies ^ (jiffies >> 7)));
@@ -3122,10 +3152,8 @@
/* NOTHING */;
rt_hash_mask--;
- for (i = 0; i <= rt_hash_mask; i++) {
- spin_lock_init(&rt_hash_table[i].lock);
- rt_hash_table[i].chain = NULL;
- }
+ memset(rt_hash_table, 0, (rt_hash_mask + 1) * sizeof(struct rt_hash_bucket));
+ rt_hash_lock_init();
ipv4_dst_ops.gc_thresh = (rt_hash_mask + 1);
ip_rt_max_size = (rt_hash_mask + 1) * 16;