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| author | Eric Dumazet <edumazet@google.com> | 2023-09-20 20:17:14 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2023-10-01 13:20:36 +0100 |
| commit | 076433bd78d719b34d465c1e69eef512036b534c (patch) | |
| tree | 6f77d1d57d8385d2f500279d653ccc51efcf63aa /include | |
| parent | ee9af4e14d166c34ec78896bb1ba545249445df0 (diff) | |
| download | lwn-076433bd78d719b34d465c1e69eef512036b534c.tar.gz lwn-076433bd78d719b34d465c1e69eef512036b534c.zip | |
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 <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/pkt_sched.h | 1 |
1 files changed, 1 insertions, 0 deletions
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 */ |