---
title: "UDP Performance Report"
---

> Documentation Index
> Fetch the complete documentation index at: https://openarkstudio.github.io/arknet/llms.txt
> Use this file to discover all available pages before exploring further.

# UDP Performance Report

Local measurements on 2026-10-12 include 504 matrix runs, 21 receive-buffer isolation runs, and a 60-second UDP stress run for each dependency configuration. Independent Release C++ programs produced these results, not CI.

## Test Conditions

| Item | Configuration |
| --- | --- |
| Machine | Mac mini Mac16,11, Apple M4 Pro, 14 cores (10 performance + 4 efficiency), 48 GiB |
| OS | macOS 27.0.1 (26A434), arm64, AC power, low-power mode disabled |
| Toolchain | Apple Clang 21.0.0, CMake 4.3.3, Ninja, C++20, Release `-O3 -DNDEBUG` |
| Dependencies | Standalone Asio 1.38.2 / Boost 1.90.0, OpenSSL 3.6.4; TLS build enabled, sanitizers disabled |
| Network | IPv4 loopback; clients and server in one process; no CPU affinity |
| Measurement | Three independent processes per configuration; 1 s measurement, 0.25 s warmup; isolation runs have no warmup |
| Socket buffers | 64 KiB send / 4 MiB receive; isolation runs vary the server receive capacity |

Matrix source SHA-256: `0771574af8ca56f1914deb544b956079e0a2f24021953ded5f5d524e3df334b1`. Isolation runs add server receive counts and a configurable receive buffer; their archive includes the patch and executable hash.

## Correctness and Load Range

| Group | Standalone | Boost | Result |
| --- | ---: | ---: | --- |
| UDP stress | 60 seconds passed | 60 seconds passed | Data and shutdown checks passed in these runs |
| IO models: 3 payloads × 2 client counts × 5 models | 90 / 90 passed | 90 / 90 passed | Window-1 performance baseline |
| Payload / batch: 3 payloads × 4 windows × 3 models | 93 / 108 passed | 93 / 108 passed | 62 valid configurations and 10 failed configurations combined |
| Size boundaries: 6 payloads × 3 windows | 36 / 54 passed | 36 / 54 passed | Large bursts exceed receive capacity |

All failed records remain archived. A failed repetition excludes all three runs of that configuration from throughput rankings.

## Throughput and Latency

1024-byte datagrams, 16 clients, one outstanding message per client, no extra computation:

![UDP throughput: medians and ranges across IO models](/arknet/performance/assets/udp-work0-throughput.svg)

![UDP p99 RTT: medians and ranges across IO models](/arknet/performance/assets/udp-work0-latency.svg)

| Dependency | io_contexts / threads | Roundtrips / s | p99 RTT / μs | Process CPU / % |
| --- | --- | ---: | ---: | ---: |
| Standalone | 1 / 1 | 92,515 | 207.79 | 99.4 |
| Standalone | 1 / 2 | 86,611 | 211.58 | 173.3 |
| Boost | 1 / 1 | 90,452 | 207.96 | 99.7 |
| Boost | 1 / 2 | 95,095 | 270.71 | 157.4 |

Standalone has the highest median throughput with one thread at this load. Boost gains some throughput with two threads, at higher p99 latency and CPU use.

Bars show medians; error bars show the minimum and maximum of three runs, not confidence intervals. CPU uses one core as 100% and includes both clients and server. Whole-machine share is process CPU% / 14.

[All IO values](/arknet/performance/udp-summary.json) · [Complete 64/1024/16384-byte results](/arknet/performance/udp) · [Payload and outstanding-window charts](/arknet/performance/dimensions-udp)

## Receive Buffer Isolation

16 clients, one context/one thread, no warmup. Each configuration runs three times; loss counts below are identical across the three repetitions.

| Payload / B | Outstanding per client | Effective server receive buffer | Total outstanding payload budget | Loss per run |
| --- | ---: | ---: | ---: | ---: |
| 16,384 | 64 | 1 MiB | 16 MiB | 959 |
| 16,384 | 64 | 2 MiB | 16 MiB | 895 |
| 16,384 | 64 | 4 MiB | 16 MiB | 767 |
| 16,384 | 16 | 4 MiB | 4 MiB | 0 |
| 16,384 | 1 | 4 MiB | 256 KiB | 0 |
| 1,472 | 64 | 4 MiB | 1.44 MiB | 0 |
| 1,024 | 1,024 | 4 MiB | 16 MiB | 12,411 |

Every run satisfies: client sends − server receives = missing datagrams; server receives = client echoes. Content and sequence errors are zero. In one 4 MiB / 16 KiB / window-64 run, the kernel's `dropped due to full socket buffers` counter increased from 152,304 to 153,071: exactly 767. IPv4 fragmentation/reassembly increases were zero.

> **Warning: Receive queue overflow**
>
> **These losses come from the server receive queue overflowing.** A large burst of small datagrams reproduces the same condition. Loopback still uses finite queues. Total outstanding payload is neither an exact instantaneous queue length nor a universal capacity threshold.

See [Buffers and flow control](/arknet/guides/socket-buffers) for configuration and the TCP/UDP distinction. Native UDP datagram semantics remain unchanged: no new default throttling, fragmentation or retransmission.

## Reproduce and Inspect Evidence

Compile using the [UDP build instructions](/arknet/features/udp/performance#build-and-run), then directly run the C++ case:

```sh
build-perf/benchmarks/arknet_loopback_benchmark \
  --protocol udp --payload 16384 --clients 16 --window 64 \
  --io-model shared --io-threads 1 --seconds 1 --warmup 0 \
  --udp-server-receive-buffer 4194304
```

This overflow probe is expected to return a nonzero status. Set the window to 16, or the payload to 1472, to reproduce the corresponding loss-free configurations above.

[Raw records, commands and machine metadata](https://github.com/OpenArkStudio/arknet/tree/main/benchmarks/results/macmini-m4pro-20261012-udp) · [Per-run kernel snapshots](https://github.com/OpenArkStudio/arknet/tree/main/benchmarks/results/macmini-m4pro-20261012-udp/buffer-probes) · [Size-boundary charts](/arknet/performance/udp-limits)

Results cover short IPv4 loopback runs on this machine. Cross-host capacity and IPv6 stress capacity are not measured. RUDP has a [separate report](/arknet/performance/rudp). Coroutine comparisons use native TCP and must not be generalized to UDP.

Source: https://openarkstudio.github.io/arknet/performance/udp-update/index.mdx