[Bridge] [PATCH net-next V6 02/14] bridge: Add vlan filtering infrastructure
Vlad Yasevich
vyasevic at redhat.com
Sun Jan 20 17:59:30 UTC 2013
On 01/17/2013 08:57 PM, Michał Mirosław wrote:
> 2013/1/16 Vlad Yasevich <vyasevic at redhat.com>:
> [...]
>> --- /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
>
More information about the Bridge
mailing list