7928a3ffb4
* Lazily load types into `Func`
This commit changes the construction of a `Func` to lazily load the type
information if required instead of always loading the type information
at `Func`-construction time. The main purpose of this change is to
accelerate instantiation of instances which have many imports. Currently
in the fast way of doing this the instantiation loop looks like:
let mut store = Store::new(&engine, ...);
let instance = instance_pre.instantiate(&mut store);
In this situation the `instance_pre` will typically load host-defined
functions (defined via `Linker` APIs) into the `Store` as individual
`Func` items and then perform the instantiation process. The operation
of loading a `HostFunc` into a `Store` however currently involves two
expensive operations:
* First a read-only lock is taken on the `RwLock` around engine
signatures.
* Next a clone of the wasm type is made to pull it out of the engine
signature registry.
Neither of these is actually necessary for imported functions. The
`FuncType` for imported functions is never used since all comparisons
happen with the intern'd indices instead. The only time a `FuncType` is
used typically is for exported functions when using `Func::typed` or
similar APIs which need type information.
This commit makes this path faster by storing `Option<FuncType>` instead
of `FuncType` within a `Func`. This means that it starts out as `None`
and is only filled in on-demand as necessary. This means that when
instantiating a module with many imports no clones/locks are done.
On a simple microbenchmark where a module with 100 imports is
instantiated this PR improves instantiation time by ~35%. Due to the
rwlock used here and the general inefficiency of pthreads rwlocks the
effect is even more profound when many threads are performing the same
instantiation process. On x86_64 with 8 threads performing instantiation
this PR improves instantiation time by 80% and on arm64 it improves by
97% (wow read-contended glibc rwlocks on arm64 are slow).
Note that much of the improvement here is also from memory
allocatoins/deallocations no longer being performed because dropping
functions within a store no longer requires deallocating the `FuncType`
if it's not present.
A downside of this PR is that `Func::ty` is now unconditionally taking
an rwlock if the type hasn't already been filled in. (it uses the
engine). If this is an issue in the future though we can investigate at
that time using somthing like a `Once` to lazily fill in even when
mutable access to the store isn't available.
* Review comments
wasmtime
A standalone runtime for WebAssembly
A Bytecode Alliance project
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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.
-
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.