3394c2bb91
This commit implements an optimization to help improve concurrently creating instances of a module on many threads simultaneously. One bottleneck to this measured has been the reference count modification on `Arc<HostFunc>`. Each host function stored within a `Linker<T>` is wrapped in an `Arc<HostFunc>` structure, and when any of those host functions are inserted into a store the reference count is incremented. When the store is dropped the reference count is then decremented. This ends up meaning that when a module imports N functions it ends up doing 2N atomic modifications over the lifetime of the instance. For embeddings where the `Linker<T>` is rarely modified but instances are frequently created this can be a surprising bottleneck to creating many instances. A change implemented here is to optimize the instantiation process when using an `InstancePre<T>`. An `InstancePre` serves as an opportunity to take the list of items used to instantiate a module and wrap them all up in an `Arc<[T]>`. Everything is going to get cloned into a `Store<T>` anyway so to optimize this the `Arc<[T]>` is cloned at the top-level and then nothing else is cloned internally. This continues to, however, preserve a strong reference count for all contained items to prevent them from being deallocated. A new variant of `FuncKind` was added for host functions which is effectively stored via `*mut HostFunc`. This variant is unsafe to create and manage and has been documented internally. Performance-wise the overall impact of this change is somewhat minor. It's already a bit esoteric if this atomic increment and decrement are a bottleneck due to the number of concurrent instances being created. In my measurements I've seen that this can reduce instantiation time by up to 10% for a module that imports two dozen functions. For larger modules with more imports this is expected to have a larger win.
wasmtime
A standalone runtime for WebAssembly
A Bytecode Alliance project
Guide | Contributing | Website | Chat
Installation
The Wasmtime CLI can be installed on Linux and macOS with a small install script:
curl https://wasmtime.dev/install.sh -sSf | bash
Windows or otherwise interested users can download installers and binaries directly from the GitHub Releases page.
Example
If you've got the Rust compiler installed then you can take some Rust source code:
fn main() {
println!("Hello, world!");
}
and compile/run it with:
$ rustup target add wasm32-wasi
$ rustc hello.rs --target wasm32-wasi
$ wasmtime hello.wasm
Hello, world!
Features
-
Lightweight. Wasmtime is a standalone runtime for WebAssembly that scales with your needs. It fits on tiny chips as well as makes use of huge servers. Wasmtime can be embedded into almost any application too.
-
Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code at runtime.
-
Configurable. Whether you need to precompile your wasm ahead of time, or interpret it at runtime, Wasmtime has you covered for all your wasm-executing needs.
-
WASI. Wasmtime supports a rich set of APIs for interacting with the host environment through the WASI standard.
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Standards Compliant. Wasmtime passes the official WebAssembly test suite, implements the official C API of wasm, and implements future proposals to WebAssembly as well. Wasmtime developers are intimately engaged with the WebAssembly standards process all along the way too.
Language Support
You can use Wasmtime from a variety of different languages through embeddings of the implementation:
- Rust - the
wasmtimecrate - C - the
wasm.h,wasi.h, andwasmtime.hheaders or usewasmtimeConan package - C++ - the
wasmtime-cpprepository or usewasmtime-cppConan package - Python - the
wasmtimePyPI package - .NET - the
WasmtimeNuGet package - Go - the
wasmtime-gorepository
Documentation
📚 Read the Wasmtime guide here! 📚
The wasmtime guide is the best starting point to learn about what Wasmtime can do for you or help answer your questions about Wasmtime. If you're curious in contributing to Wasmtime, it can also help you do that!
It's Wasmtime.