Re: ARP does not scale

[Tim Gardner <timg@tpi.com>]

On Saturday 13 March 2004 16:32, Anton Blanchard wrote:
> [moving this to netdev]

Anton,

I figured out how to subscribe.

> It would be nice to fix this properly in 2.6, a CONFIG option for this sort
> of thing is painful for distros.
>
> Check out net/ipv4/tcp.c and how it makes an effort to scale tcp_ehash and
> tcp_bhash with memory and also allows an override with a cmdline option
> thash_entries.
>
> Anton
>

I checked out how tcp_ehash and tcp_bhash auto-size based on the amount of 
RAM. I think one can usually make the same assumption about the relative 
number of ARP entries. I say usually because I have some core routers that 
have over a thousand ARP entries. In that case I would like to override the 
auto-size calculation so that I can force enough hash buckets such that there 
is never (or rarely) a hash collision.

How about a compromise. Leave in the config option, but default it to 0 which 
enables the auto-size algorithm. Otherwise, use the size specified in the 
config option. 

rtg
-- 
Tim Gardner - timg@tpi.com
www.tpi.com 406-443-5357