From 10da66f7552b3c7966c2f4f1f72009fb0b5539ec Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 13 Oct 2010 08:22:03 +0000 Subject: 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 Signed-off-by: David S. Miller --- net/ipv4/fib_frontend.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c index 919f2ad19b49..3df057e89640 100644 --- a/net/ipv4/fib_frontend.c +++ b/net/ipv4/fib_frontend.c @@ -1016,16 +1016,15 @@ static struct notifier_block fib_netdev_notifier = { 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; + + /* 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( - sizeof(struct hlist_head)*FIB_TABLE_HASHSZ, GFP_KERNEL); + 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; -- cgit v1.2.3