On 01/17/2013 08:57 PM, Michał Mirosław wrote:
2013/1/16 Vlad Yasevich <vyasevic@xxxxxxxxxx>:
[...]
--- /dev/null
+++ b/net/bridge/br_vlan.c
[...]
+struct net_port_vlan *nbp_vlan_find(const struct net_port_vlans *v, u16 vid)
+{
+ struct net_port_vlan *pve;
+
+ /* Must be done either in rcu critical section or with RTNL held */
+ WARN_ON_ONCE(!rcu_read_lock_held() && !rtnl_is_locked());
+
+ list_for_each_entry_rcu(pve, &v->vlan_list, list) {
+ if (pve->vid == vid)
+ return pve;
+ }
+
+ return NULL;
+}
This looks expensive - it's O(n) with n = number of configured VLANs on a port.
And this is called for every packet. The bridge already has a hash of VLAN
structures found by br_vlan_find(). You could add a second bitmap there
(eg. ingres_ports[]) and check port's bit instead of walking the list.
You would use a bit more memory (64 bytes minus the removed list-head)
per configured VLAN but save some cycles in hot path.
Technically wouldn't even need another bitmap as an existing membership
bitmap would cover this case. I did some profiling and the list is
faster for 3 vlans per port. Hash is faster for more then 3 vlans.
I can easily switch to hash if that is what others think.
-vlad
Best Regards,
Michał Mirosław
