Re: [B.A.T.M.A.N.] [PATCH v2 5/5] batman-adv: B.A.T.M.A.N. V - implement GW selection logic

[Antonio Quartulli <a@unstable.cc>]

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On Fri, May 13, 2016 at 07:31:01PM +0800, Marek Lindner wrote:
> On Tuesday, May 10, 2016 18:06:09 Antonio Quartulli wrote:
> > +static int batadv_v_gw_throughput_get(struct batadv_gw_node *gw_node, u32
> > *bw)
> 
> > +static struct batadv_gw_node *
> > +batadv_v_gw_get_best_gw_node(struct batadv_priv *bat_priv)
> 
> Kernel doc ?

ok :)

> 
> 
> > +	struct batadv_gw_node *gw_node, *curr_gw = NULL;
> > +	u32 max_bw = 0, bw, threshold;
> > +
> > +	threshold = atomic_read(&bat_priv->gw.sel_class);
> > +
> > +	rcu_read_lock();
> > +	hlist_for_each_entry_rcu(gw_node, &bat_priv->gw.list, list) {
> > +		if (!kref_get_unless_zero(&gw_node->refcount))
> > +			continue;
> > +
> > +		if (batadv_v_gw_throughput_get(gw_node, &bw) < 0)
> > +			goto next;
> > +
> > +		if (curr_gw && (bw <= (max_bw + threshold)))
> > +			goto next;
> > +
> > +		if (curr_gw)
> > +			batadv_gw_node_put(curr_gw);
> > +
> > +		curr_gw = gw_node;
> > +		kref_get(&curr_gw->refcount);
> > +		max_bw = bw;
> > +
> > +next:
> > +		batadv_gw_node_put(gw_node);
> > +	}
> > +	rcu_read_unlock();
> > +
> > +	return curr_gw;
> > +}
> 
> I don't quite follow the use of 'threshold' in this function. The threshold is 
> meant to decide whether the switch to another gateway is worth breaking the 
> existing stateful connections. Here, the code is retrieving the best gateway 
> of all - no need for the threshold ? Moreover, the threshold might lead to 
> unpredictable results. If the threshold is 5 MBit/s and the first gateway in 
> the list offers 1 MBit/s while the second offers 5 MBit/s the better gateway 
> is never chosen. 

You are right. I will re-work this part.

> 
> 
> > +static bool batadv_v_gw_is_eligible(struct batadv_priv *bat_priv,
> > +				    struct batadv_orig_node *curr_gw_orig,
> > +				    struct batadv_orig_node *orig_node)
> 
> > +/* fails if orig_node has no router */
> > +static int batadv_v_gw_write_buffer_text(struct batadv_priv *bat_priv,
> > +					 struct seq_file *seq,
> > +					 const struct batadv_gw_node *gw_node)
> 
> > +static void batadv_v_gw_print(struct batadv_priv *bat_priv,
> > +			      struct seq_file *seq)
> 
> More room for kernel doc ..

there is always room for kerneldoc..

> 
> 
> > @@ -387,7 +569,16 @@ static struct batadv_algo_ops batadv_batman_v
> > __read_mostly = { */
> >  int batadv_v_mesh_init(struct batadv_priv *bat_priv)
> >  {
> > -	return batadv_v_ogm_init(bat_priv);
> > +	int ret = 0;
> > +
> > +	ret = batadv_v_ogm_init(bat_priv);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* set default throughput difference threshold to 5Mbps */
> > +	atomic_set(&bat_priv->gw.sel_class, 50);
> > +
> > +	return 0;
> >  }
> 
> There is no need to initial 'ret' if the next line is setting a proper value.
> If you moved the atomic_set() above the batadv_v_ogm_init() call most of the 
> chachacha would go away.
> 

mhhh ok!

> In batadv_softif_init_late() bat_priv->gw.sel_class is initialized for 
> B.A.T.M.A.N. IV. Do you intend to keep it there ? If not, a per-routing 
> algorithm init might be cleaner ..  :)
> 

I do agree :)

I'll rework this part too.

Thanks !

Cheers,




-- 
Antonio Quartulli

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