netdev - On 5.6.2, SCTP is 10 000 times slower than TCP

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Message-ID: <09cc102b-31d1-b0e8-3ea1-3b07b9a6df74@yandex.ru>
Date:   Thu, 9 Apr 2020 17:09:26 +0300
From:   Konstantin Kharlamov <hi-angel@...dex.ru>
To:     netdev@...r.kernel.org
Subject: On 5.6.2, SCTP is 10 000 times slower than TCP

I was considering, whether SCTP could be faster than TCP, and made some
measurements. Results are astonishing: 4.74 GB/sec for TCP vs 590, KB/sec for
SCTP. Let me rephrase: that is 4.74 GB/sec vs 0.00059 GB/sec! Wow. This looks
sooo wrong, that this is probably a bug, so I'm reporting it here.

Tests are done on kernel 5.6.2 with qperf 0.4.11 as follows:

1. Run `qperf` in one terminal
2. Run `qperf -v localhost tcp_bw tcp_lat sctp_bw sctp_lat` in the other terminal

Below are 4 results for my Dell Inspiron 5767 laptop.

Test number | TCP bandwidth | TCP latency, μs | SCTP bandwidth | SCTP latency, μs
1           | 4.74 GB/sec   | 6.81            | 590, KB/sec    | 11.8
2           | 5 GB/sec      | 6.79            | 721, KB/sec    | 10.5
3           | 4.73 GB/sec   | 6.76            | 8.39, MB/sec   | 10.9
4           | 5.7 GB/sec    | 6.1             | 53.4, MB/sec   | 9.33

FWIW, I also made some measurements on a server hw with older kernel 4.19. The
difference there is not that big, yet even there SCTP is twice as slower compared
to TCP.

P.S.: please add me to CC when replying as I'm not subscribed to the list.