Re: [PATCH net-next-2.6 v3] net_sched: SFB flow scheduler

Le mercredi 23 février 2011 à 17:24 +0100, Patrick McHardy a écrit :

This needs to be a per-skb property, otherwise you could have the
situation:

- enqueue skb, double_buffering=0, increment buffer 0
- enable double buffering
- swap buffers
- dequeue same skb, decrement buffer 1

after which the qlen values of buffer 1 will be incorrect.

Normally its OK, because we bzero() the zone, and the "decrement" is
0-bounded.

I had this idea (of storing two bits per skb), but :

- It means that swap_buffer() should not touch (bzero) the 'old' bins

- Since hash perturbator is changed, we have to store the two hash
values per skb (instead of one u32 / classid).

quoted

+		slot ^= 1;
+		sfbhash = sfb_hash(skb, slot, q);

Isn't there room in the cb to store both hash values?

Yes, I am going to implement your idea, its probably OK to use two u32
on skb_cb for this.

Thanks !