Re: tx queue hashing hot-spots and poor performance (multiq, ixgbe)

[David Miller <davem@davemloft.net>]

From: Andrew Dickinson <andrew@whydna.net>
Date: Thu, 30 Apr 2009 07:04:33 -0700

>  I'll do some debugging around skb_tx_hash() and see if I can make
> sense of it.  I'll let you know what I find.  My hypothesis is that
> skb_record_rx_queue() isn't being called, but I should dig into it
> before I start making claims. ;-P

That's one possibility.

Another is that the hashing isn't working out.  One way to
play with that is to simply replace the:

		hash = skb_get_rx_queue(skb);

in skb_tx_hash() with something like:

		return skb_get_rx_queue(skb) % dev->real_num_tx_queues;

and see if that improves the situation.