net_sched: sch_fq: always garbage collect

FQ performs garbage collection at enqueue time, and only
if number of flows is above a given threshold, which
is hit after the qdisc has been used a bit.

Since an RB-tree traversal is needed to locate a flow,
it makes sense to perform gc all the time, to keep
rb-trees smaller.

This reduces by 50 % average storage costs in FQ,
and avoids 1 cache line miss at enqueue time when
fast path added in prior patch can not be used.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_fq.c

@@ -367,9 +367,7 @@ static struct fq_flow *fq_classify(struct Qdisc *sch, struct sk_buff *skb)
 
 	root = &q->fq_root[hash_ptr(sk, q->fq_trees_log)];
 
-	if (q->flows >= (2U << q->fq_trees_log) &&
-	    q->inactive_flows > q->flows/2)
-		fq_gc(q, root, sk);
+	fq_gc(q, root, sk);
 
 	p = &root->rb_node;
 	parent = NULL;