From 520ac30f45519b0a82dd92117c181d1d6144677b Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 21 Jun 2016 23:16:49 -0700 Subject: net_sched: drop packets after root qdisc lock is released Qdisc performance suffers when packets are dropped at enqueue() time because drops (kfree_skb()) are done while qdisc lock is held, delaying a dequeue() draining the queue. Nominal throughput can be reduced by 50 % when this happens, at a time we would like the dequeue() to proceed as fast as possible. Even FQ is vulnerable to this problem, while one of FQ goals was to provide some flow isolation. This patch adds a 'struct sk_buff **to_free' parameter to all qdisc->enqueue(), and in qdisc_drop() helper. I measured a performance increase of up to 12 %, but this patch is a prereq so that future batches in enqueue() can fly. Signed-off-by: Eric Dumazet Acked-by: Jesper Dangaard Brouer Signed-off-by: David S. Miller --- net/sched/sch_choke.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) (limited to 'net/sched/sch_choke.c') diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c index 789b69ee9e51..3b6d5bd69101 100644 --- a/net/sched/sch_choke.c +++ b/net/sched/sch_choke.c @@ -115,7 +115,8 @@ static void choke_zap_tail_holes(struct choke_sched_data *q) } /* Drop packet from queue array by creating a "hole" */ -static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx) +static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx, + struct sk_buff **to_free) { struct choke_sched_data *q = qdisc_priv(sch); struct sk_buff *skb = q->tab[idx]; @@ -129,7 +130,7 @@ static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx) qdisc_qstats_backlog_dec(sch, skb); qdisc_tree_reduce_backlog(sch, 1, qdisc_pkt_len(skb)); - qdisc_drop(skb, sch); + qdisc_drop(skb, sch, to_free); --sch->q.qlen; } @@ -261,7 +262,8 @@ static bool choke_match_random(const struct choke_sched_data *q, return choke_match_flow(oskb, nskb); } -static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch) +static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch, + struct sk_buff **to_free) { int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS; struct choke_sched_data *q = qdisc_priv(sch); @@ -288,7 +290,7 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch) /* Draw a packet at random from queue and compare flow */ if (choke_match_random(q, skb, &idx)) { q->stats.matched++; - choke_drop_by_idx(sch, idx); + choke_drop_by_idx(sch, idx, to_free); goto congestion_drop; } @@ -331,16 +333,16 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch) } q->stats.pdrop++; - return qdisc_drop(skb, sch); + return qdisc_drop(skb, sch, to_free); congestion_drop: - qdisc_drop(skb, sch); + qdisc_drop(skb, sch, to_free); return NET_XMIT_CN; other_drop: if (ret & __NET_XMIT_BYPASS) qdisc_qstats_drop(sch); - kfree_skb(skb); + __qdisc_drop(skb, to_free); return ret; } -- cgit v1.2.3-59-g8ed1b