f5041dd362
* Implement a setting for reserved dynamic memory growth Dynamic memories aren't really that heavily used in Wasmtime right now because for most 32-bit memories they're classified as "static" which means they reserve 4gb of address space and never move. Growth of a static memory is simply making pages accessible, so it's quite fast. With the memory64 feature, however, this is no longer true since all memory64 memories are classified as "dynamic" at this time. Previous to this commit growth of a dynamic memory unconditionally moved the entire linear memory in the host's address space, always resulting in a new `Mmap` allocation. This behavior is causing fuzzers to time out when working with 64-bit memories because incrementally growing a memory by 1 page at a time can incur a quadratic time complexity as bytes are constantly moved. This commit implements a scheme where there is now a tunable setting for memory to be reserved at the end of a dynamic memory to grow into. This means that dynamic memory growth is ideally amortized as most calls to `memory.grow` will be able to grow into the pre-reserved space. Some calls, though, will still need to copy the memory around. This helps enable a commented out test for 64-bit memories now that it's fast enough to run in debug mode. This is because the growth of memory in the test no longer needs to copy 4gb of zeros. * Test fixes & review comments * More comments
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.
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Configurable. Whether you need to precompile your wasm ahead of time, generate code blazingly fast with Lightbeam, or interpret it at runtime, Wasmtime has you covered for all your wasm-executing needs.
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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 - [C++] - the
wasmtime-cpprepository - 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.