3419f63575
This fixes a very complicated bug (b/246). Evaluation
progresses *much* further after this, leading to several less
complicated bugs likely being uncovered by this
What was the problem?
=====================
Previously, when evaluating a thunk, we had a code path that looked
like this:
match *thunk {
ThunkRepr::Evaluated(Value::Thunk(ref inner_thunk)) => {
let inner_repr = inner_thunk.0.borrow().clone();
drop(thunk);
self.0.replace(inner_repr);
}
/* ... */
}
This code path created a copy of the inner `ThunkRepr` of a nested
thunk, and moved that copy into the `ThunkRepr` of the parent.
The effect of this was that the original `ThunkRepr` (unforced!) lived
on in the original thunk, without the memoization of the subsequent
forcing applying to it.
This had the result that Tvix would repeatedly evaluate these thunks
without ever memoizing them, if they occured repeatedly as shared
inner thunks. Most notably, this would *always* occur when
builtins.import was used.
What's the solution?
====================
I have completely rewritten `Thunk::force_trampoline_self` to make all
flows that can occur in it explicit. I have also removed the outer
loop inside of that function, and resorted to more use of trampolining
instead.
The function is now well-commented and it should be possible to read
it from top-to-bottom and get a general sense of what is going on,
though the trampolining itself (which is implemented in the VM) needs
to be at least partially understood for this.
What's the new problem(s)?
==========================
One new (known) problem is that we have to construct `Error` instances
in all error types here, but we do not have spans available in some
thunk-related situations. Due to b/238 we cannot ask the VM for an
arbitrary span from the callsite leading to the force. This means that
there are now code paths where, under certain conditions, causing an
evaluation error during thunk forcing will panic.
To fix this we will need to investigate and fix b/238, and/or add a
span tracking mechanism to thunks themselves.
What other impacts does this have?
==================================
With this commit, eval of nixpkgs mostly succeeds (things like stdenv
evaluate to the same hashes for us and C++ Nix, meaning we now
construct identical derivations without eval breaking).
Due to this we progress much further into nixpkgs, which lets us
uncover more additional bugs. For example, after this commit we can
quickly see that cl/7949 introduces some kind of behavioural issue and
should not be merged as-is (this was not apparent before).
Additionally, tvix-eval is now seemingly very fast. When doing
performance analysis of a nixpkgs eval, we now mostly see the code
path for shelling out to C++ Nix to add things to the store in there.
We still need those code paths, so we can not (yet) do a performance
analysis beyond that.
Change-Id: I738525bad8bc5ede5d8c737f023b14b8f4160612
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8012
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
|
||
|---|---|---|
| .gcroots | ||
| .nixery | ||
| corp | ||
| docs | ||
| fun | ||
| lisp | ||
| net | ||
| nix | ||
| ops | ||
| third_party | ||
| tools | ||
| tvix | ||
| users | ||
| views | ||
| web | ||
| .envrc | ||
| .git-blame-ignore-revs | ||
| .gitignore | ||
| .hgignore | ||
| .mailmap | ||
| .rgignore | ||
| buf.gen.yaml | ||
| buf.yaml | ||
| default.nix | ||
| LICENSE | ||
| OWNERS | ||
| README.md | ||
| RULES | ||
| rustfmt.toml | ||
depot
This repository is the monorepo for the community around The Virus Lounge, containing our personal tools and infrastructure. Everything in here is built using Nix.
A large portion of the software here is very self-referential, meaning that it exists to sustain the operation of the repository. This is the case because we partially see this as an experiment in tooling for monorepos.
Highlights
Services
-
Source code is available primarily through Sourcegraph on cs.tvl.fyi, where it is searchable and even semantically indexed. A lower-tech view of the repository is also available via cgit-pink on code.tvl.fyi.
The repository can be cloned using
gitfromhttps://cl.tvl.fyi/depot. -
All code in the depot, with the exception of code that is checked in to individual
//usersfolders, needs to be reviewed. We use Gerrit on cl.tvl.fyi for this. -
Issues are tracked via our own issue tracker on b.tvl.fyi. Its source code lives at
//web/panettone/. -
Smaller todo-list entries which do not warrant a separate issue are listed at todo.tvl.fyi.
-
We use Buildkite for CI. Recent builds are listed on tvl.fyi/builds and pipelines are configured dynamically via
//ops/pipelines. -
A search service that makes TVL services available via textual shortcuts is available: atward
All services that we host are deployed on NixOS machines that we manage. Their
configuration is tracked in //ops/{modules,machines}.
Nix
//nix/readTreecontains the Nix code which automatically registers projects in our Nix attribute hierarchy based on their in-tree location//tools/nixerycontains the source code of Nixery, a container registry that can build images ad-hoc from Nix packages//nix/yantscontains Yet Another Nix Type System, which we use for a variety of things throughout the repository//nix/buildGoimplements a Nix library that can build Go software in the style of Bazel'srules_go. Go programs in this repository are built using this library.//nix/buildLispimplements a Nix library that can build Common Lisp software. Currently only SBCL is supported. Lisp programs in this repository are built using this library.//web/blogand//web/atom-feed: A Nix-based static site generator which generates the web page and Atom feed for tazj.in (//users/tazjin/homepage) and tvl.fyi (//web/tvl)//web/bubblegumcontains a CGI-based web framework written in Nix.//nix/nint: A shebang-compatible interpreter wrapper for Nix.//tvixcontains initial work towards a modular architecture for Nix.
We have a variety of other tools and libraries in the //nix folder which may
be of interest.
Packages / Libraries
//net/alcoholic_jwtcontains an easy-to-use JWT-validation library for Rust//net/crimpcontains a high-level HTTP client using cURL for Rust//tools/emacs-pkgscontains various useful Emacs libraries, for example:dottime.elprovides dottime in the Emacs modelinenix-util.elprovides editing utilities for Nix filesterm-switcher.elis an ivy-function for switching between vterm bufferstvl.elprovides helper functions for interacting with the TVL monorepo
//lisp/klatreprovides a grab-bag utility library for Common Lisp
User packages
Contributors to the repository have user directories under
//users, which can be used for
personal or experimental code that does not require review.
Some examples:
//users/grfn/xanthous: A (WIP) TUI RPG, written in Haskell.//users/tazjin/emacs: tazjin's Emacs & EXWM configuration//users/tazjin/finito: A persistent finite-state machine library for Rust.
Licensing
Unless otherwise stated in a subdirectory, all code is licensed under the MIT license. See LICENSE for details.
Contributing
If you'd like to contribute to any of the tools in here, please check out the contribution guidelines and our code of conduct.
IRC users can find us in #tvl on hackint, which is also
reachable via XMPP at #tvl@irc.hackint.org (sic!).
Hackint also provide a web chat.