Brad Fitzpatrick ad5436af0d tstest/largetailnet, tstest/integration/testcontrol: add in-process large-tailnet benchmark
Add a Go benchmark that exercises a single tailnet client (a [tsnet.Server]
running in the test process) against a synthetic large initial netmap and
a stream of caller-driven peer add/remove deltas, all in-process.

The harness is split in two parts:

  - tstest/largetailnet, a reusable package containing a [Streamer]
    that hijacks the map long-poll on a [testcontrol.Server] via the new
    AltMapStream hook, sends one initial MapResponse with N synthetic
    peers, and forwards caller-supplied delta MapResponses on the same
    stream. Helpers like MakePeer / AllocPeer build synthetic peers with
    unique IDs and addresses derived from the Tailscale ULA range.

  - tstest/largetailnet/largetailnet_test.go, BenchmarkGiantTailnet
    (headless tailscaled workload, no IPN bus subscriber) and
    BenchmarkGiantTailnetBusWatcher (GUI-client workload with one
    Notify subscriber attached). Both are gated on
    --actually-test-giant-tailnet (skipped by default), stand up an
    in-process testcontrol + tsnet.Server, let Up block until the
    initial N-peer netmap has been processed, then ResetTimer and run
    add+remove pairs via b.Loop. Per-delta sync is via a test-only
    [ipnlocal.LocalBackend.AwaitNodeKeyForTest] channel that closes
    once the just-added peer key appears in the netmap (no-watcher
    variant) or via bus-Notify drain (bus-watcher variant).

To support the hijack, [testcontrol.Server] grows an AltMapStream hook
and a small MapStreamWriter interface for benchmarks/stress tests that
need to drive a controlled MapResponse sequence; the normal serveMap
path is untouched when AltMapStream is nil. The streamer answers
non-streaming "lite" map polls (which controlclient issues before the
streaming long-poll to push HostInfo) with an empty MapResponse and
returns immediately, so the streaming poll that follows is the one
that gets the initial netmap.

The benchmark is intended for before/after comparisons of netmap- and
delta-handling changes targeted at large tailnets. CPU profiles on
unmodified main show the expected O(N) hotspots:
setControlClientStatusLocked / authReconfigLocked /
userspaceEngine.Reconfig / setNetMapLocked, plus JSON encoding of the
full Notify.NetMap to bus watchers (which dominates the BusWatcher
variant).

Median ms/op over 10 runs on unmodified main, by tailnet size N:

       N      no-watcher   bus-watcher
   10000          32          166
   50000         222          865
  100000         504         1765
  250000        1551         4696

Recommended invocation:

	go test ./tstest/largetailnet/ -run=^$ \
	    -bench='BenchmarkGiantTailnet(BusWatcher)?$' \
	    -benchtime=2000x -timeout=10m \
	    --actually-test-giant-tailnet \
	    --giant-tailnet-n=250000 \
	    -cpuprofile=/tmp/giant.cpu.pprof

Updates #12542

Change-Id: I4f5b2bb271a36ba853d5a0ffe82054ef2b15c585
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2026-04-27 11:47:12 -07:00

Tailscale

https://tailscale.com

Private WireGuard® networks made easy

Overview

This repository contains the majority of Tailscale's open source code. Notably, it includes the tailscaled daemon and the tailscale CLI tool. The tailscaled daemon runs on Linux, Windows, macOS, and to varying degrees on FreeBSD and OpenBSD. The Tailscale iOS and Android apps use this repo's code, but this repo doesn't contain the mobile GUI code.

Other Tailscale repos of note:

For background on which parts of Tailscale are open source and why, see https://tailscale.com/opensource/.

Using

We serve packages for a variety of distros and platforms at https://pkgs.tailscale.com.

Other clients

The macOS, iOS, and Windows clients use the code in this repository but additionally include small GUI wrappers. The GUI wrappers on non-open source platforms are themselves not open source.

Building

We always require the latest Go release, currently Go 1.26. (While we build releases with our Go fork, its use is not required.)

go install tailscale.com/cmd/tailscale{,d}

If you're packaging Tailscale for distribution, use build_dist.sh instead, to burn commit IDs and version info into the binaries:

./build_dist.sh tailscale.com/cmd/tailscale
./build_dist.sh tailscale.com/cmd/tailscaled

If your distro has conventions that preclude the use of build_dist.sh, please do the equivalent of what it does in your distro's way, so that bug reports contain useful version information.

Bugs

Please file any issues about this code or the hosted service on the issue tracker.

Contributing

PRs welcome! But please file bugs. Commit messages should reference bugs.

We require Developer Certificate of Origin Signed-off-by lines in commits.

See commit-messages.md (or skim git log) for our commit message style.

About Us

Tailscale is primarily developed by the people at https://github.com/orgs/tailscale/people. For other contributors, see:

WireGuard is a registered trademark of Jason A. Donenfeld.

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