8a55b5c563
This PR introduces a new way of performing cooperative timeslicing that is intended to replace the "fuel" mechanism. The tradeoff is that this mechanism interrupts with less precision: not at deterministic points where fuel runs out, but rather when the Engine enters a new epoch. The generated code instrumentation is substantially faster, however, because it does not need to do as much work as when tracking fuel; it only loads the global "epoch counter" and does a compare-and-branch at backedges and function prologues. This change has been measured as ~twice as fast as fuel-based timeslicing for some workloads, especially control-flow-intensive workloads such as the SpiderMonkey JS interpreter on Wasm/WASI. The intended interface is that the embedder of the `Engine` performs an `engine.increment_epoch()` call periodically, e.g. once per millisecond. An async invocation of a Wasm guest on a `Store` can specify a number of epoch-ticks that are allowed before an async yield back to the executor's event loop. (The initial amount and automatic "refills" are configured on the `Store`, just as for fuel.) This call does only signal-safe work (it increments an `AtomicU64`) so could be invoked from a periodic signal, or from a thread that wakes up once per period.
61 lines
1.4 KiB
Rust
61 lines
1.4 KiB
Rust
mod async_functions;
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mod call_hook;
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mod cli_tests;
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mod custom_signal_handler;
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mod debug;
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mod epoch_interruption;
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mod externals;
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mod fuel;
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mod func;
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mod funcref;
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mod gc;
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mod globals;
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mod host_funcs;
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mod iloop;
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mod import_calling_export;
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mod import_indexes;
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mod instance;
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mod invoke_func_via_table;
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mod limits;
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mod linker;
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mod memory;
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mod memory_creator;
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mod module;
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mod module_linking;
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mod module_serialize;
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mod name;
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mod pooling_allocator;
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mod relocs;
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mod stack_overflow;
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mod store;
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mod table;
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mod traps;
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mod wast;
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/// A helper to compile a module in a new store with reference types enabled.
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pub(crate) fn ref_types_module(
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source: &str,
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) -> anyhow::Result<(wasmtime::Store<()>, wasmtime::Module)> {
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use wasmtime::*;
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let _ = env_logger::try_init();
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let mut config = Config::new();
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config.wasm_reference_types(true);
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let engine = Engine::new(&config)?;
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let store = Store::new(&engine, ());
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let module = Module::new(&engine, source)?;
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Ok((store, module))
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}
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/// A helper determining whether the pooling allocator tests should be skipped.
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pub(crate) fn skip_pooling_allocator_tests() -> bool {
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// There are a couple of issues when running the pooling allocator tests under QEMU:
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// - high memory usage that may exceed the limits imposed by the environment (e.g. CI)
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// - https://github.com/bytecodealliance/wasmtime/pull/2518#issuecomment-747280133
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std::env::var("WASMTIME_TEST_NO_HOG_MEMORY").is_ok()
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}
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