keeping ifindex in 16bits or does it have to be sparse?

keeping ifindex in 16bits or does it have to be sparse?

[Jeremy Jackson]

The question came up when profiling Quagga... a performance issue occurs
because it's iterating over a linked list of interface structures... and
this person is using 2000 interfaces for ADSL PPPoE server.  It's an
interesting use case.

There are 2 options to make the interface lookup in quagga scale: array
or hash.  My first thought was array, but it seems that ifindex can get
sparse, that is, the largest ifindex can be much bigger (eg 408589) the
number of max number of interfaces.

So question to netdev, is it possible to reuse ifindex eventually, so it
won't keep growing with interface add/delete, and are there
(unnecessary) large jumps in the allocation sequence?

-- 
Jeremy Jackson
Coplanar Networks
(519)489-4903
http://www.coplanar.net
jerj@coplanar.net

Re: keeping ifindex in 16bits or does it have to be sparse?

[Ben Greear]

Jeremy Jackson wrote:
> The question came up when profiling Quagga... a performance issue occurs
> because it's iterating over a linked list of interface structures... and
> this person is using 2000 interfaces for ADSL PPPoE server.  It's an
> interesting use case.
>
> There are 2 options to make the interface lookup in quagga scale: array
> or hash.  My first thought was array, but it seems that ifindex can get
> sparse, that is, the largest ifindex can be much bigger (eg 408589) the
> number of max number of interfaces.
>
> So question to netdev, is it possible to reuse ifindex eventually, so it
> won't keep growing with interface add/delete, and are there
> (unnecessary) large jumps in the allocation sequence?
>   
Please use a hash...I'm sure someone will have a use-case with more than 
64k interfaces
sometime soon.

Ben

-- 
Ben Greear <greearb@candelatech.com> 
Candela Technologies Inc  http://www.candelatech.com

Re: keeping ifindex in 16bits or does it have to be sparse?

[Stephen Hemminger]

On Tue, 31 Mar 2009 11:08:17 -0400
Jeremy Jackson <jerj@coplanar.net> wrote:

> The question came up when profiling Quagga... a performance issue occurs
> because it's iterating over a linked list of interface structures... and
> this person is using 2000 interfaces for ADSL PPPoE server.  It's an
> interesting use case.
> 
> There are 2 options to make the interface lookup in quagga scale: array
> or hash.  My first thought was array, but it seems that ifindex can get
> sparse, that is, the largest ifindex can be much bigger (eg 408589) the
> number of max number of interfaces.
> 
> So question to netdev, is it possible to reuse ifindex eventually, so it
> won't keep growing with interface add/delete, and are there
> (unnecessary) large jumps in the allocation sequence?
> 

Hash the names as well, since quagga does a lot of lookup by name.