fib: avoid false sharing on fib_table_hash
While doing profile analysis, I found fib_hash_table was sometime in a
cache line shared by a possibly often written kernel structure.
(CONFIG_IP_ROUTE_MULTIPATH || !CONFIG_IPV6_MULTIPLE_TABLES)
It's hard to detect because not easily reproductible.
Make sure we allocate a full cache line to keep this shared in all cpus
caches.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 919f2ad..3df057e 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1016,16 +1016,15 @@
static int __net_init ip_fib_net_init(struct net *net)
{
int err;
- unsigned int i;
+ size_t size = sizeof(struct hlist_head) * FIB_TABLE_HASHSZ;
- net->ipv4.fib_table_hash = kzalloc(
- sizeof(struct hlist_head)*FIB_TABLE_HASHSZ, GFP_KERNEL);
+ /* Avoid false sharing : Use at least a full cache line */
+ size = max_t(size_t, size, L1_CACHE_BYTES);
+
+ net->ipv4.fib_table_hash = kzalloc(size, GFP_KERNEL);
if (net->ipv4.fib_table_hash == NULL)
return -ENOMEM;
- for (i = 0; i < FIB_TABLE_HASHSZ; i++)
- INIT_HLIST_HEAD(&net->ipv4.fib_table_hash[i]);
-
err = fib4_rules_init(net);
if (err < 0)
goto fail;
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index b6a5859..de38211 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1500,15 +1500,18 @@
static int __net_init fib6_net_init(struct net *net)
{
+ size_t size = sizeof(struct hlist_head) * FIB6_TABLE_HASHSZ;
+
setup_timer(&net->ipv6.ip6_fib_timer, fib6_gc_timer_cb, (unsigned long)net);
net->ipv6.rt6_stats = kzalloc(sizeof(*net->ipv6.rt6_stats), GFP_KERNEL);
if (!net->ipv6.rt6_stats)
goto out_timer;
- net->ipv6.fib_table_hash = kcalloc(FIB6_TABLE_HASHSZ,
- sizeof(*net->ipv6.fib_table_hash),
- GFP_KERNEL);
+ /* Avoid false sharing : Use at least a full cache line */
+ size = max_t(size_t, size, L1_CACHE_BYTES);
+
+ net->ipv6.fib_table_hash = kzalloc(size, GFP_KERNEL);
if (!net->ipv6.fib_table_hash)
goto out_rt6_stats;