Re: netif_rx packet dumping

["David S. Miller" <davem@davemloft.net>]

On Thu, 3 Mar 2005 12:38:11 -0800
Stephen Hemminger <shemminger@osdl.org> wrote:

> The existing throttling algorithm causes all packets to be dumped
> (until queue emptys) when the packet backlog reaches
> netdev_max_backog. I suppose this is some kind of DoS prevention
> mechanism. The problem is that this dumping action creates mulitple
> packet loss that forces TCP back to slow start.
> 
> But, all this is really moot for the case of any reasonably high speed
> device because of NAPI. netif_rx is not even used for any device that
> uses NAPI.  The NAPI code path uses net_receive_skb and the receive
> queue management is done by the receive scheduling (dev->quota) of the
> rx_scheduler.

Even without NAPI, netif_rx() ends up using the quota etc. machanisms
when the queue gets processed via process_backlog().

ksoftirqd should handle cpu starvation issues at a higher level.

I think it is therefore safe to remove the netif_max_backlog stuff
altogether.  "300" is such a non-sense setting, especially for gigabit
drivers which aren't using NAPI for whatever reason.  It's even low
for a system with 2 100Mbit devices.