Mercurial > hg
view rust/README.rst @ 48598:a6f16ec07ed7
stream-clone: add a explicit test for format change during stream clone
They are different kind of requirements, the one which impact the data storage
and are relevant to the files being streamed and the one which does not. For
example some requirements are only relevant to the working copy, like sparse, or
dirstate-v2.
Since they are irrelevant to the content being streamed, they do not prevent the
receiving side to use streaming clone and mercurial skip adverting them over
the wire and, ideally, within the bundle.
In addition, this let the client decide to use whichever format it desire for
the part that does not affect the store itself. So the configuration related to
these format are used as normal when doing a streaming clone.
In practice, the feature was not really tested and is badly broken with bundle-2,
since the requirements are not filtered out from the stream bundle.
So we start with adding simple tests as a good base before the fix and adjust
the feature.
Differential Revision: https://phab.mercurial-scm.org/D12029
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
---|---|
date | Mon, 17 Jan 2022 18:51:47 +0100 |
parents | 799fdf4cca80 |
children | 649ff7f86f96 |
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=================== Mercurial Rust Code =================== This directory contains various Rust code for the Mercurial project. Rust is not required to use (or build) Mercurial, but using it improves performance in some areas. There are currently four independent Rust projects: - chg. An implementation of chg, in Rust instead of C. - hgcli. A project that provides a (mostly) self-contained "hg" binary, for ease of deployment and a bit of speed, using PyOxidizer. See hgcli/README.md. - hg-core (and hg-cpython): implementation of some functionality of mercurial in Rust, e.g. ancestry computations in revision graphs, status or pull discovery. The top-level ``Cargo.toml`` file defines a workspace containing these crates. - rhg: a pure Rust implementation of Mercurial, with a fallback mechanism for unsupported invocations. It reuses the logic `hg-core` but completely forgoes interaction with Python. See `rust/rhg/README.md` for more details. Using Rust code =============== Local use (you need to clean previous build artifacts if you have built without rust previously):: $ make PURE=--rust local # to use ./hg $ ./tests/run-tests.py --rust # to run all tests $ ./hg debuginstall | grep -i rust # to validate rust is in use checking Rust extensions (installed) checking module policy (rust+c-allow) If the environment variable ``HGWITHRUSTEXT=cpython`` is set, the Rust extension will be used by default unless ``--no-rust``. One day we may use this environment variable to switch to new experimental binding crates like a hypothetical ``HGWITHRUSTEXT=hpy``. Special features ================ You might want to check the `features` section in ``hg-cpython/Cargo.toml``. It may contain features that might be interesting to try out. To use features from the Makefile, use the `HG_RUST_FEATURES` environment variable: for instance `HG_RUST_FEATURES="some-feature other-feature"` Profiling ========= Setting the environment variable ``RUST_LOG=trace`` will make hg print a few high level rust-related performance numbers. It can also indicate why the rust code cannot be used (say, using lookarounds in hgignore). Creating a ``.cargo/config`` file with the following content enables debug information in optimized builds. This make profiles more informative with source file name and line number for Rust stack frames and (in some cases) stack frames for Rust functions that have been inlined. [profile.release] debug = true ``py-spy`` (https://github.com/benfred/py-spy) can be used to construct a single profile with rust functions and python functions (as opposed to ``hg --profile``, which attributes time spent in rust to some unlucky python code running shortly after the rust code, and as opposed to tools for native code like ``perf``, which attribute time to the python interpreter instead of python functions). Example usage: $ make PURE=--rust local # Don't forget to recompile after a code change $ py-spy record --native --output /tmp/profile.svg -- ./hg ... Developing Rust =============== The current version of Rust in use is ``1.48.0``, because it's what Debian stable has. You can use ``rustup override set 1.48.0`` at the root of the repo to make it easier on you. Go to the ``hg-cpython`` folder:: $ cd rust/hg-cpython Or, only the ``hg-core`` folder. Be careful not to break compatibility:: $ cd rust/hg-core Simply run:: $ cargo build --release It is possible to build without ``--release``, but it is not recommended if performance is of any interest: there can be an order of magnitude of degradation when removing ``--release``. For faster builds, you may want to skip code generation:: $ cargo check For even faster typing:: $ cargo c You can run only the rust-specific tests (as opposed to tests of mercurial as a whole) with:: $ cargo test --all Formatting the code ------------------- We use ``rustfmt`` to keep the code formatted at all times. For now, we are using the nightly version because it has been stable enough and provides comment folding. To format the entire Rust workspace:: $ cargo +nightly fmt This requires you to have the nightly toolchain installed.