b73ac83c37
As first suggested by Jan on the Zulip here [1], a cheap and effective way to obtain copy-on-write semantics of a "backing image" for a Wasm memory is to mmap a file with `MAP_PRIVATE`. The `memfd` mechanism provided by the Linux kernel allows us to create anonymous, in-memory-only files that we can use for this mapping, so we can construct the image contents on-the-fly then effectively create a CoW overlay. Furthermore, and importantly, `madvise(MADV_DONTNEED, ...)` will discard the CoW overlay, returning the mapping to its original state. By itself this is almost enough for a very fast instantiation-termination loop of the same image over and over, without changing the address space mapping at all (which is expensive). The only missing bit is how to implement heap *growth*. But here memfds can help us again: if we create another anonymous file and map it where the extended parts of the heap would go, we can take advantage of the fact that a `mmap()` mapping can be *larger than the file itself*, with accesses beyond the end generating a `SIGBUS`, and the fact that we can cheaply resize the file with `ftruncate`, even after a mapping exists. So we can map the "heap extension" file once with the maximum memory-slot size and grow the memfd itself as `memory.grow` operations occur. The above CoW technique and heap-growth technique together allow us a fastpath of `madvise()` and `ftruncate()` only when we re-instantiate the same module over and over, as long as we can reuse the same slot. This fastpath avoids all whole-process address-space locks in the Linux kernel, which should mean it is highly scalable. It also avoids the cost of copying data on read, as the `uffd` heap backend does when servicing pagefaults; the kernel's own optimized CoW logic (same as used by all file mmaps) is used instead. [1] https://bytecodealliance.zulipchat.com/#narrow/stream/206238-general/topic/Copy.20on.20write.20based.20instance.20reuse/near/266657772
128 lines
3.5 KiB
TOML
128 lines
3.5 KiB
TOML
[package]
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name = "wasmtime-cli"
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version = "0.33.0"
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authors = ["The Wasmtime Project Developers"]
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description = "Command-line interface for Wasmtime"
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license = "Apache-2.0 WITH LLVM-exception"
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documentation = "https://bytecodealliance.github.io/wasmtime/cli.html"
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categories = ["wasm"]
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keywords = ["webassembly", "wasm"]
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repository = "https://github.com/bytecodealliance/wasmtime"
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readme = "README.md"
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edition = "2018"
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default-run = "wasmtime"
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[lib]
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doctest = false
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[[bin]]
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name = "wasmtime"
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path = "src/bin/wasmtime.rs"
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doc = false
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[dependencies]
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wasmtime = { path = "crates/wasmtime", version = "0.33.0", default-features = false, features = ['cache', 'cranelift'] }
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wasmtime-cache = { path = "crates/cache", version = "=0.33.0" }
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wasmtime-cranelift = { path = "crates/cranelift", version = "=0.33.0" }
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wasmtime-environ = { path = "crates/environ", version = "=0.33.0" }
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wasmtime-wast = { path = "crates/wast", version = "=0.33.0" }
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wasmtime-wasi = { path = "crates/wasi", version = "0.33.0" }
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wasmtime-wasi-crypto = { path = "crates/wasi-crypto", version = "0.33.0", optional = true }
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wasmtime-wasi-nn = { path = "crates/wasi-nn", version = "0.33.0", optional = true }
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structopt = { version = "0.3.5", features = ["color", "suggestions"] }
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anyhow = "1.0.19"
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target-lexicon = { version = "0.12.0", default-features = false }
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pretty_env_logger = "0.4.0"
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file-per-thread-logger = "0.1.1"
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libc = "0.2.60"
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rayon = "1.5.0"
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humantime = "2.0.0"
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wasmparser = "0.81.0"
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lazy_static = "1.4.0"
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[target.'cfg(unix)'.dependencies]
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rustix = "0.31.0"
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[dev-dependencies]
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# depend again on wasmtime to activate its default features for tests
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wasmtime = { path = "crates/wasmtime", version = "0.33.0" }
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env_logger = "0.8.1"
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filecheck = "0.5.0"
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more-asserts = "0.2.1"
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tempfile = "3.1.0"
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test-programs = { path = "crates/test-programs" }
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wasmtime-runtime = { path = "crates/runtime" }
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tokio = { version = "1.8.0", features = ["rt", "time", "macros", "rt-multi-thread"] }
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tracing-subscriber = "0.3.1"
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wast = "38.0.0"
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criterion = "0.3.4"
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num_cpus = "1.13.0"
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winapi = { version = "0.3.9", features = ['memoryapi'] }
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memchr = "2.4"
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async-trait = "0.1"
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wat = "1.0.40"
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[build-dependencies]
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anyhow = "1.0.19"
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[profile.release.build-override]
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opt-level = 0
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[workspace]
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resolver = '2'
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members = [
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"cranelift",
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"cranelift/isle/fuzz",
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"cranelift/isle/islec",
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"cranelift/serde",
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"crates/bench-api",
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"crates/c-api",
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"crates/misc/run-examples",
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"examples/fib-debug/wasm",
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"examples/wasi/wasm",
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"examples/tokio/wasm",
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"fuzz",
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]
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exclude = [
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'crates/wasi-common/WASI/tools/witx-cli',
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'docs/rust_wasi_markdown_parser'
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]
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[features]
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default = ["jitdump", "wasmtime/wat", "wasmtime/parallel-compilation", "wasi-nn"]
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jitdump = ["wasmtime/jitdump"]
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vtune = ["wasmtime/vtune"]
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wasi-crypto = ["wasmtime-wasi-crypto"]
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wasi-nn = ["wasmtime-wasi-nn"]
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uffd = ["wasmtime/uffd"]
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pooling-allocator = ["wasmtime/pooling-allocator"]
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memfd-allocator = ["pooling-allocator", "wasmtime/memfd-allocator"]
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all-arch = ["wasmtime/all-arch"]
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posix-signals-on-macos = ["wasmtime/posix-signals-on-macos"]
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# Stub feature that does nothing, for Cargo-features compatibility: the new
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# backend is the default now.
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experimental_x64 = []
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[badges]
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maintenance = { status = "actively-developed" }
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[[test]]
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name = "host_segfault"
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harness = false
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[[example]]
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name = "tokio"
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required-features = ["wasmtime-wasi/tokio"]
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[profile.dev.package.backtrace]
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debug = false # FIXME(#1813)
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[[bench]]
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name = "instantiation"
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harness = false
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[[bench]]
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name = "thread_eager_init"
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harness = false
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