From: Stephen Hemminger <stephen@networkplumber•org>
To: vyasevic@redhat•com
Cc: "Michał Mirosław" <mirqus@gmail•com>,
netdev@vger•kernel.org, bridge@lists•linux-foundation.org,
davem@davemloft•net, shemminger@vyatta•com, mst@redhat•com,
shmulik.ladkani@gmail•com
Subject: Re: [PATCH net-next V6 02/14] bridge: Add vlan filtering infrastructure
Date: Sun, 20 Jan 2013 11:38:25 -0800 [thread overview]
Message-ID: <20130120113825.759b4a58@nehalam.linuxnetplumber.net> (raw)
In-Reply-To: <50FC307A.5090003@redhat.com>
On Sun, 20 Jan 2013 12:59:22 -0500
Vlad Yasevich <vyasevic@redhat•com> wrote:
> On 01/17/2013 08:57 PM, Michał Mirosław wrote:
> > 2013/1/16 Vlad Yasevich <vyasevic@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
Let's assume the people that really want this feature are using a lot
of vlan's. i.e n = 1000 or so. A bitmap is O(1). Any hash list would
incur a just a big memory penalty for the list head. In other words
a full bitmap is 4096 bits = 512 bytes. If you use hash list,
then the equivalent memory size would be only 64 list heads, therefore
a bitmap is a better choice than a hlist.
next prev parent reply other threads:[~2013-01-20 19:39 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-16 18:17 [PATCH net-next V6 00/14] Add basic VLAN support to bridges Vlad Yasevich
2013-01-16 18:17 ` [PATCH net-next V6 01/14] vlan: wrap hw-acceleration calls in separate functions Vlad Yasevich
2013-01-16 22:00 ` Michał Mirosław
2013-01-16 22:03 ` Michał Mirosław
2013-01-16 18:17 ` [PATCH net-next V6 02/14] bridge: Add vlan filtering infrastructure Vlad Yasevich
2013-01-17 4:47 ` Cong Wang
2013-01-18 1:57 ` Michał Mirosław
2013-01-20 17:59 ` Vlad Yasevich
2013-01-20 19:38 ` Stephen Hemminger [this message]
2013-01-21 1:50 ` Vlad Yasevich
2013-01-21 11:45 ` Shmulik Ladkani
2013-01-22 14:31 ` Vlad Yasevich
2013-01-22 15:55 ` Shmulik Ladkani
2013-01-22 16:27 ` Vlad Yasevich
[not found] ` <CB4696DA7737D0409230B481D0363B1414F0E6029D@HQ1-EXCH03.corp.brocade.com>
[not found] ` <20130122091746.7a3820e9@nehalam.linuxnetplumber.net>
2013-01-22 17:32 ` Vlad Yasevich
2013-01-20 21:38 ` Shmulik Ladkani
2013-01-21 1:56 ` Vlad Yasevich
2013-01-16 18:17 ` [PATCH net-next V6 03/14] bridge: Validate that vlan is permitted on ingress Vlad Yasevich
2013-01-20 22:27 ` Shmulik Ladkani
2013-01-21 1:58 ` Vlad Yasevich
2013-01-16 18:17 ` [PATCH net-next V6 04/14] bridge: Verify that a vlan is allowed to egress on give port Vlad Yasevich
2013-01-16 18:18 ` [PATCH net-next V6 05/14] bridge: Cache vlan in the cb for faster egress lookup Vlad Yasevich
2013-01-16 18:18 ` [PATCH net-next V6 06/14] bridge: Add netlink interface to configure vlans on bridge ports Vlad Yasevich
2013-01-17 4:54 ` Cong Wang
2013-01-17 5:52 ` David Miller
2013-01-16 18:18 ` [PATCH net-next V6 07/14] bridge: Add the ability to configure pvid Vlad Yasevich
2013-01-16 18:18 ` [PATCH net-next V6 08/14] bridge: Implement vlan ingress/egress policy Vlad Yasevich
2013-01-16 18:18 ` [PATCH net-next V6 09/14] bridge: API to configure egress policy Vlad Yasevich
2013-01-16 18:18 ` [PATCH net-next V6 10/14] bridge: Add vlan to unicast fdb entries Vlad Yasevich
2013-01-16 18:18 ` [PATCH net-next V6 11/14] bridge: Add vlan id to multicast groups Vlad Yasevich
2013-01-16 18:18 ` [PATCH net-next V6 12/14] bridge: Add vlan support to static neighbors Vlad Yasevich
2013-01-17 5:16 ` Cong Wang
2013-01-16 18:18 ` [PATCH net-next V6 13/14] bridge: Add vlan support for local fdb entries Vlad Yasevich
2013-01-16 18:18 ` [PATCH net-next V6 14/14] bridge: Dump vlan information from a bridge port Vlad Yasevich
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