From 076433bd78d719b34d465c1e69eef512036b534c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 20 Sep 2023 20:17:14 +0000 Subject: net_sched: sch_fq: add fast path for mostly idle qdisc TCQ_F_CAN_BYPASS can be used by few qdiscs. Idea is that if we queue a packet to an empty qdisc, following dequeue() would pick it immediately. FQ can not use the generic TCQ_F_CAN_BYPASS code, because some additional checks need to be performed. This patch adds a similar fast path to FQ. Most of the time, qdisc is not throttled, and many packets can avoid bringing/touching at least four cache lines, and consuming 128bytes of memory to store the state of a flow. After this patch, netperf can send UDP packets about 13 % faster, and pktgen goes 30 % faster (when FQ is in the way), on a fast NIC. TCP traffic is also improved, thanks to a reduction of cache line misses. I have measured a 5 % increase of throughput on a tcp_rr intensive workload. tc -s -d qd sh dev eth1 ... qdisc fq 8004: parent 1:2 limit 10000p flow_limit 100p buckets 1024 orphan_mask 1023 quantum 3028b initial_quantum 15140b low_rate_threshold 550Kbit refill_delay 40ms timer_slack 10us horizon 10s horizon_drop Sent 5646784384 bytes 1985161 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0 flows 122 (inactive 122 throttled 0) gc 0 highprio 0 fastpath 659990 throttled 27762 latency 8.57us Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/uapi/linux/pkt_sched.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/uapi/linux/pkt_sched.h') diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h index 3f85ae578056..579f641846b8 100644 --- a/include/uapi/linux/pkt_sched.h +++ b/include/uapi/linux/pkt_sched.h @@ -962,6 +962,7 @@ struct tc_fq_qd_stats { __u64 ce_mark; /* packets above ce_threshold */ __u64 horizon_drops; __u64 horizon_caps; + __u64 fastpath_packets; }; /* Heavy-Hitter Filter */ -- cgit v1.2.3