From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Puranjay Mohan" <puranjay@kernel.org>, <bpf@vger.kernel.org>
Cc: "Puranjay Mohan" <puranjay12@gmail.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Martin KaFai Lau" <martin.lau@kernel.org>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Mykyta Yatsenko" <mykyta.yatsenko5@gmail.com>,
"Fei Chen" <feichen@meta.com>,
"Taruna Agrawal" <taragrawal@meta.com>,
"Nikhil Dixit Limaye" <ndixit@meta.com>,
"Nikita V. Shirokov" <tehnerd@tehnerd.com>,
<kernel-team@meta.com>
Subject: Re: [RFC PATCH bpf-next 0/6] selftests/bpf: Add XDP load-balancer benchmark
Date: Tue, 21 Apr 2026 18:16:36 -0700 [thread overview]
Message-ID: <DHZAC1DIKBSJ.2CO1A8NY2B2EM@gmail.com> (raw)
In-Reply-To: <20260420111726.2118636-1-puranjay@kernel.org>
On Mon Apr 20, 2026 at 4:17 AM PDT, Puranjay Mohan wrote:
> Sample single-scenario output:
>
> $ sudo ./bench -a -w3 -p1 xdp-lb --scenario tcp-v4-lru-miss
> Calibration: 84 ns/op, batch_iters=119047 (~9ms/batch)
why print this?
> Proportionality check: 2N/N ratio=1.9996 (ok)
why print this?
> Validating scenario 'tcp-v4-lru-miss' (batch_iters=119047):
why print batch_iters ?
> [tcp-v4-lru-miss] PASS (XDP_TX) IPv4 TCP, LRU miss (16M flow space), CH lookup
> Flow diversity: 16777216 unique src addrs (mask 0xffffff)
why print this?
> Cold LRU: enabled (per-batch generation)
>
> Scenario: tcp-v4-lru-miss - IPv4 TCP, LRU miss (16M flow space), CH lookup
> Batch size: 119047 iterations/invocation (+1 for validation)
and then print them again to hammer the point ?!
> In-BPF timing: 203 samples, 119047 ops/batch
and 3rd time to really annoy humans.
> median 856.8 ns/op, stddev 39.4, CV 4.54% [min 817.4, max 1173.6]
> p50 856.8, p75 881.4, p90 918.3, p95 943.3, p99 976.3
> NOTE: right-skewed distribution (tail 3.6x the body)
Too much data. What humans suppose to do with all of that?
>
> Distribution (ns/op):
> <p1 : 1 (below range)
> 820 : 4 |*** |
> 830 : 31 |***************************** |
> 840 : 42 |****************************************|
> 850 : 33 |******************************* |
> 860 : 25 |*********************** |
> 870 : 15 |************** |
> 880 : 8 |******* |
> 890 : 14 |************* |
> 900 : 6 |***** |
> 910 : 6 |***** |
> 920 : 2 |* |
> 930 : 5 |**** |
> 940 : 2 |* |
> 950 : 3 |** |
> 960 : 2 |* |
> 970 : 2 |* |
> >p99 : 2 (above range)
I frankly don't see a point.
It proves that bell curve exists. So? I would remove it completely.
>
> Sample run script output:
>
> $ ./benchs/run_bench_xdp_lb.sh
>
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | Single-flow baseline | n | p50 | stddev | CV | min | p90 | p99 | max |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | tcp-v4-lru-hit | 202 | 83.14 | 0.16 | 0.19% | 82.79 | 83.31 | 83.51 | 83.60 |
> | tcp-v4-ch | 201 | 92.26 | 0.12 | 0.13% | 92.05 | 92.41 | 92.57 | 92.68 |
> | tcp-v6-lru-hit | 202 | 81.00 | 0.12 | 0.14% | 80.80 | 81.15 | 81.45 | 81.56 |
> | tcp-v6-ch | 201 | 106.36 | 0.14 | 0.13% | 106.07 | 106.55 | 106.73 | 107.03 |
> | udp-v4-lru-hit | 202 | 114.65 | 0.17 | 0.15% | 114.22 | 114.85 | 115.02 | 115.06 |
> | udp-v6-lru-hit | 297 | 112.91 | 0.17 | 0.15% | 112.56 | 113.13 | 113.45 | 113.50 |
> | tcp-v4v6-lru-hit | 298 | 81.28 | 1.11 | 1.37% | 80.09 | 82.04 | 86.32 | 86.71 |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | Diverse flows (4K src addrs) | n | p50 | stddev | CV | min | p90 | p99 | max |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | tcp-v4-lru-diverse | 272 | 93.43 | 0.38 | 0.40% | 92.76 | 93.92 | 94.97 | 95.30 |
> | tcp-v4-ch-diverse | 291 | 94.92 | 1.88 | 1.97% | 94.08 | 97.70 | 102.66 | 102.86 |
> | tcp-v6-lru-diverse | 270 | 89.43 | 1.85 | 2.06% | 88.42 | 91.34 | 99.04 | 100.00 |
> | tcp-v6-ch-diverse | 291 | 108.85 | 0.23 | 0.21% | 108.58 | 109.04 | 110.26 | 110.73 |
> | udp-v4-lru-diverse | 268 | 126.66 | 2.04 | 1.60% | 124.95 | 129.11 | 137.47 | 138.29 |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | TCP flags | n | p50 | stddev | CV | min | p90 | p99 | max |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | tcp-v4-syn | 204 | 787.60 | 0.92 | 0.12% | 785.53 | 788.68 | 790.23 | 791.21 |
> | tcp-v4-rst-miss | 226 | 160.33 | 1.12 | 0.70% | 158.67 | 161.71 | 164.23 | 164.92 |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | LRU stress | n | p50 | stddev | CV | min | p90 | p99 | max |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | tcp-v4-lru-miss | 203 | 855.68 | 31.97 | 3.71% | 813.63 | 908.00 | 952.04 | 979.49 |
> | udp-v4-lru-miss | 211 | 854.79 | 48.24 | 5.55% | 819.49 | 928.10 | 1061.91 | 1129.39 |
> | tcp-v4-lru-warmup | 286 | 534.18 | 16.62 | 3.09% | 510.34 | 559.55 | 592.37 | 594.51 |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | Early exits | n | p50 | stddev | CV | min | p90 | p99 | max |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
> | pass-v4-no-vip | 210 | 25.80 | 0.04 | 0.15% | 25.72 | 25.85 | 25.88 | 26.04 |
> | pass-v6-no-vip | 282 | 27.67 | 0.06 | 0.20% | 27.60 | 27.73 | 27.96 | 28.00 |
> | pass-v4-icmp | 215 | 5.57 | 0.06 | 1.12% | 5.47 | 5.67 | 5.76 | 5.77 |
> | pass-non-ip | 207 | 4.80 | 0.10 | 2.14% | 4.67 | 4.94 | 5.18 | 5.23 |
> | drop-v4-frag | 207 | 4.81 | 0.02 | 0.48% | 4.79 | 4.85 | 4.88 | 4.89 |
> | drop-v4-options | 206 | 4.82 | 0.09 | 1.95% | 4.74 | 5.00 | 5.17 | 5.24 |
> | drop-v6-frag | 201 | 4.93 | 0.09 | 1.89% | 4.86 | 5.11 | 5.21 | 5.36 |
> +----------------------------------+------+----------+---------+--------+----------+----------+----------+----------+
Too much data.
prev parent reply other threads:[~2026-04-22 1:16 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-20 11:17 [RFC PATCH bpf-next 0/6] selftests/bpf: Add XDP load-balancer benchmark Puranjay Mohan
2026-04-20 11:17 ` [RFC PATCH bpf-next 1/6] selftests/bpf: Add bench_force_done() for early benchmark completion Puranjay Mohan
2026-04-20 12:41 ` sashiko-bot
2026-04-20 15:32 ` Mykyta Yatsenko
2026-04-20 11:17 ` [RFC PATCH bpf-next 2/6] selftests/bpf: Add BPF batch-timing library Puranjay Mohan
2026-04-20 13:18 ` sashiko-bot
2026-04-22 1:10 ` Alexei Starovoitov
2026-04-20 11:17 ` [RFC PATCH bpf-next 3/6] selftests/bpf: Add XDP load-balancer common definitions Puranjay Mohan
2026-04-20 13:26 ` sashiko-bot
2026-04-20 11:17 ` [RFC PATCH bpf-next 4/6] selftests/bpf: Add XDP load-balancer BPF program Puranjay Mohan
2026-04-20 13:57 ` sashiko-bot
2026-04-20 11:17 ` [RFC PATCH bpf-next 5/6] selftests/bpf: Add XDP load-balancer benchmark driver Puranjay Mohan
2026-04-20 17:11 ` sashiko-bot
2026-04-20 11:17 ` [RFC PATCH bpf-next 6/6] selftests/bpf: Add XDP load-balancer benchmark run script Puranjay Mohan
2026-04-20 17:36 ` sashiko-bot
2026-04-22 1:16 ` Alexei Starovoitov [this message]
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