d6c57eb957
This replaces the OpCode enum with a new Op enum which is guaranteed to fit in a
single byte. Instead of carrying enum variants with data, every variant that has
runtime data encodes it into the `Vec<u8>` that a `Chunk` now carries.
This has several advantages:
* Less stack space is required at runtime, and fewer allocations are required
while compiling.
* The OpCode doesn't need to carry "weird" special-cased data variants anymore.
* It is faster (albeit, not by much). On my laptop, results consistently look
approximately like this:
Benchmark 1: ./before -E '(import <nixpkgs> {}).firefox.outPath' --log-level ERROR --no-warnings
Time (mean ± σ): 8.224 s ± 0.272 s [User: 7.149 s, System: 0.688 s]
Range (min … max): 7.759 s … 8.583 s 10 runs
Benchmark 2: ./after -E '(import <nixpkgs> {}).firefox.outPath' --log-level ERROR --no-warnings
Time (mean ± σ): 8.000 s ± 0.198 s [User: 7.036 s, System: 0.633 s]
Range (min … max): 7.718 s … 8.334 s 10 runs
See notes below for why the performance impact might be less than expected.
* It is faster while at the same time dropping some optimisations we previously
performed.
This has several disadvantages:
* The code is closer to how one would write it in C or Go.
* Bit shifting!
* There is (for now) slightly more code than before.
On performance I have the following thoughts at the moment:
In order to prepare for adding GC, there's a couple of places in Tvix where I'd
like to fence off certain kinds of complexity (such as mutating bytecode, which,
for various reaons, also has to be part of data that is subject to GC). With
this change, we can drop optimisations like retroactively modifying existing
bytecode and *still* achieve better performance than before.
I believe that this is currently worth it to pave the way for changes that are
more significant for performance.
In general this also opens other avenues of optimisation: For example, we can
profile which argument sizes actually exist and remove the copy overhead of
varint decoding (which does show up in profiles) by using more adequately sized
types for, e.g., constant indices.
Known regressions:
* Op::Constant is no longer printing its values in disassembly (this can be
fixed, I just didn't get around to it, will do separately).
Change-Id: Id9b3a4254623a45de03069dbdb70b8349e976743
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12191
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
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|---|---|---|
| .. | ||
| .vscode | ||
| boot | ||
| build | ||
| build-go | ||
| castore | ||
| castore-go | ||
| cli | ||
| docs | ||
| eval | ||
| glue | ||
| nar-bridge | ||
| nix-compat | ||
| nix-lang-test-suite | ||
| scripts | ||
| serde | ||
| store | ||
| store-go | ||
| tools | ||
| tracing | ||
| verify-lang-tests | ||
| website | ||
| .gitignore | ||
| buildkite.yml | ||
| Cargo.lock | ||
| Cargo.nix | ||
| Cargo.toml | ||
| clippy.toml | ||
| crate-hashes.json | ||
| default.nix | ||
| LICENSE | ||
| logo.webp | ||
| OWNERS | ||
| README.md | ||
| shell.nix | ||
| utils.nix | ||
Tvix is a new implementation of the Nix language and package manager. See the announcement post for information about the background of this project.
Tvix is developed by TVL in our monorepo, the depot, at
//tvix. Code reviews take place on Gerrit, bugs are
filed in our issue tracker.
For more information about Tvix, feel free to reach out. We are interested in people who would like to help us review designs, brainstorm and describe requirements that we may not yet have considered.
Most of the discussion around development happens in our dedicated IRC channel,
#tvix-dev on hackint,
which is also reachable via XMPP
at #tvix-dev@irc.hackint.org (sic!)
and via Matrix at #tvix-dev:hackint.org.
There's also the IRC channel of the wider TVL community, less on-topic, or our mailing list.
Contributions to Tvix follow the TVL review flow and contribution guidelines.
WARNING: Tvix is not ready for use in production. None of our current APIs should be considered stable in any way.
WARNING: Any other instances of this project or repository are
josh-mirrors. We do not accept code contributions or issues outside of
the tooling and communication methods outlined above.
Components
This folder contains the following components:
//tvix/castore- subtree storage/transfer in a content-addressed fashion//tvix/cli- preliminary REPL & CLI implementation for Tvix//tvix/eval- an implementation of the Nix programming language//tvix/nar-bridge- a HTTP webserver providing a Nix HTTP Binary Cache interface in front of a tvix-store//tvix/nix-compat- a Rust library for compatibility with C++ Nix, features like encodings and hashing schemes and formats//tvix/serde- a Rust library for using the Nix language for app configuration//tvix/store- a "filesystem" linking Nix store paths and metadata with the content-addressed layer
Some additional folders with auxiliary things exist and can be explored at your leisure.
Building the CLI
The CLI can also be built with standard Rust tooling (i.e. cargo build),
as long as you are in a shell with the right dependencies.
- If you cloned the full monorepo, it can be provided by
mg shell //tvix:shell. - If you cloned the
tvixworkspace only (git clone https://code.tvl.fyi/depot.git:workspace=views/tvix.git),nix-shellprovides it.
If you're in the TVL monorepo, you can also run mg build //tvix/cli
(or mg build from inside that folder) for a more incremental build.
Please follow the depot-wide instructions on how to get mg and use the depot
tooling.
Compatibility
Important note: We only use and test Nix builds of our software against Nix 2.3. There are a variety of bugs and subtle problems in newer Nix versions which we do not have the bandwidth to address, builds in newer Nix versions may or may not work.
Rust projects, crate2nix
Some parts of Tvix are written in Rust. To simplify the dependency
management on the Nix side of these builds, we use crate2nix in a
single Rust workspace in //tvix to maintain the Nix build
configuration.
When making changes to Cargo dependency configuration in any of the
Rust projects under //tvix, be sure to run
mg run //tools:crate2nix-generate in //tvix itself and commit the changes
to the generated Cargo.nix file. This only applies to the full TVL checkout.
When adding/removing a Cargo feature for a crate, you will want to add it to the
features power set that gets tested in CI. For each crate there's a default.nix with a
mkFeaturePowerset invocation, modify the list to include/remove the feature.
Note that you don't want to add "collection" features, such as fs for tvix-[ca]store or default.
License structure
All code implemented for Tvix is licensed under the GPL-3.0, with the exception of the protocol buffer definitions used for communication between services which are available under a more permissive license (MIT).
The idea behind this structure is that any direct usage of our code (e.g. linking to it, embedding the evaluator, etc.) will fall under the terms of the GPL3, but users are free to implement their own components speaking these protocols under the terms of the MIT license.