Re: Route cache performance

[Simon Kirby <sim@netnation.com>]

On Fri, Aug 26, 2005 at 09:49:11PM +0200, Robert Olsson wrote:

> Hello!
> 
> This thread seems familar :)
> 
> I think Simon uses UP and it could be idea to check if the RCU deferred 
> deletion causes the problem. 
>...
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -485,7 +485,11 @@ static struct file_operations rt_cpu_seq
>  static __inline__ void rt_free(struct rtable *rt)
>  {
>  	multipath_remove(rt);
> +#ifdef CONFIG_SMP
>  	call_rcu_bh(&rt->u.dst.rcu_head, dst_rcu_free);
> +#else
> +	dst_free((struct dst_entry *)rt);
> +#endif
>  }
>  
>  static __inline__ void rt_drop(struct rtable *rt)

Woot!

Yes, this is the difference.  With the patch applied (ajust directly
freeing the dst_entry), everything balances easily, there are no
overflows, and the result of rt_may_expire() looks very reasonable.
(Yay!)

So, this seems to be the culprit.  Is NAPI supposed to allow the
queued bh to run or should we just not be queuing this?

Simon-