netdev - [PATCH net-next 4/4] net_sched: sch

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Date: Wed, 20 Sep 2023 12:54:18 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Willem de Bruijn <willemb@...gle.com>, Jamal Hadi Salim <jhs@...atatu.com>, 
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 4/4] 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@...gle.com>
---
 net/sched/sch_fq.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index ea510003bc385148397a690c5afd9387fba9796c..0fe2e90af14c2ef822a1455f3c308f0caeb53fe3 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -366,9 +366,7 @@ 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;
-- 
2.42.0.459.ge4e396fd5e-goog