nottinygc was an interesting experiment to bring OK performance to Wasm binaries compiled with Go. But there are fundamental issues with using GC languages in a sandboxed environment like Wasm - this still applies even after the Wasm GC proposal, and is even worse before it. The wasilibs recommendation is to use a non-GC language such as C++, Rust, or similar, when compiling to Wasm and to not use Go.

nottinygc

nottinygc requires TinyGo 0.28+

nottinygc is a replacement memory allocator for TinyGo targetting WASI. The default allocator is built for small code size which can cause performance issues in higher-scale use cases. nottinygc replaces it with bdwgc for garbage collection and mimalloc for standard malloc-based allocation. These mature libraries can dramatically improve the performance of TinyGo WASI applications at the expense of several hundred KB of additional code footprint.

Note that this library currently only works when the scheduler is disabled.

Usage

Using the library requires both importing it and modifying flags when invoking TinyGo.

Add a blank import to the library to your code's main package.

import _ "github.com/wasilibs/nottinygc"

Additionally, add -gc=custom and -tags=custommalloc to your TinyGo build flags.

tinygo build -o main.wasm -gc=custom -tags=custommalloc -target=wasi -scheduler=none main.go

Using with Envoy

This library relies on WASI to implement certain functionality, for which Envoy's implementation is incomplete, and in addition, it's ABI, proxy-wasm has design issues that prevent working with defaults appropriate for normal TinyGo applications. As this project is commonly used with Envoy, we provide a build tag, to work around these issues. If building an Envoy plugin, add -tags=nottinygc_envoy (or combine it with additional tags) to your TinyGo build flags. This will disable export of malloc/free/ and define a no-op sched_yield function.

Other hosts that implement WASI fully, such as wazero and ABIs with correct memory semantics, such as http-wasm, will not have any issue. Implementations of proxy-wasm other than Envoy may also work fine without the build tag.

Performance

Benchmarks are run against every commit in the bench workflow. GitHub action runners are highly virtualized and do not have stable performance across runs, but the relative numbers within a run should still be somewhat, though not precisely, informative.

One run looks like this

BenchmarkGC/bench.wasm-2         	      52	 220294559 ns/op
BenchmarkGC/benchref.wasm-2      	       6	2000167805 ns/op

The benchmark is very simple, allocating some large strings in a loop. We see nottinygc perform almost 10x better in this benchmark. Note that just allocation / collection time is not the only aspect of GC performance, allocation locality and fragmentation can also affect performance of real-world applications. We have found that the default allocator can cause applications to run out of memory, possibly due to fragmentation, whereas this library will continue to run indefinitely.