0def0f19bd
The (*SubscriberFunc[T]).dispatch method body — a ~40-line select
loop with slow-subscriber timer, snapshot handling, ctx-cancel
draining, and a CI stack-dump branch — was previously fully
duplicated by the Go compiler for every distinct GC shape of T.
None of that body actually depends on T except for the type
assertion and the user callback invocation.
This change moves the loop body into a non-generic dispatchFunc()
helper, leaving (*SubscriberFunc[T]).dispatch as a tiny wrapper
that:
- performs the vals.Peek().Event.(T) type assertion
- spawns the callback goroutine via `go runFuncCallback(s.read,
t, callDone)` — a regular generic function call, not a closure,
so that `go` binds the args to the goroutine's frame instead of
allocating a closure on the heap. This preserves the
zero-extra-allocation behavior of the original
(*SubscriberFunc[T]).runCallback method.
- resolves T's name via reflect.TypeFor[T]().String() (cached on
the stack rather than recomputed on each %T formatting)
- calls dispatchFunc with the callDone channel
The %T formatting in the original logf calls is replaced with %s
on the resolved name string, removing per-T fmt instantiations.
A new BenchmarkBasicFuncThroughput is added alongside the existing
BenchmarkBasicThroughput so per-event allocation behavior on the
SubscribeFunc dispatch path is covered by the benchmark suite.
Measured impact (util/eventbus/sizetest):
SubscriberFunc per-flow attribution:
linux/amd64: 912.5 B/flow -> 840.8 B/flow (-71.7 B/flow)
linux/arm64: 917.5 B/flow -> 849.9 B/flow (-67.6 B/flow)
The total per-flow size delta on amd64 dropped from 3,096.6 B to
3,039.2 B (-57 B/flow). The arm64 total stayed at 3,145.7 B
because the linker's page-aligned section sizing absorbed the
improvement on this binary; the symcost-attributed per-receiver
number is the real signal.
Behavior is unchanged: BenchmarkBasicThroughput stays at 0
allocs/op and BenchmarkBasicFuncThroughput holds at the same 2
allocs/op, 144 B/op as the prior eventbus implementation. All
eventbus tests pass.
Updates #12614
Change-Id: I85f933f50f58cd25bbfe5cc46bdda7aab22f0bf7
Signed-off-by: James Tucker <james@tailscale.com>
Tailscale
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:
- the Android app is at https://github.com/tailscale/tailscale-android
- the Synology package is at https://github.com/tailscale/tailscale-synology
- the QNAP package is at https://github.com/tailscale/tailscale-qpkg
- the Chocolatey packaging is at https://github.com/tailscale/tailscale-chocolatey
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:
- https://github.com/tailscale/tailscale/graphs/contributors
- https://github.com/tailscale/tailscale-android/graphs/contributors
Legal
WireGuard is a registered trademark of Jason A. Donenfeld.