This is an archive of the discontinued Mercurial Phabricator instance.

Differential D9625

rust: document how to enable debug information in optimized builds
ClosedPublic

Authored by SimonSapin on Dec 17 2020, 6:29 AM.

Details

Reviewers
pulkit
Group Reviewers
hg-reviewers
Commits
rHGec14c37958ec: rust: document how to enable debug information in optimized builds
Summary

This is particularly useful when profiling.

Diff Detail

Repository
rHG Mercurial
Branch
default
Lint
No Linters Available
Unit
No Unit Test Coverage

Event Timeline

SimonSapin created this revision.Dec 17 2020, 6:29 AM
pulkit accepted this revision.Dec 17 2020, 6:41 AM
This revision is now accepted and ready to land.Dec 17 2020, 6:41 AM

Revision Contents
Changeset List

PathPackages
M.hgignore (4 lines)
Mrust/README.rst (15 lines)

Diff 24321

.hgignore

hgext/__index__.py hgext/__index__.py
rust/target/ rust/target/
rust/*/target/ rust/*/target/
# Generated wheels # Generated wheels
wheelhouse/ wheelhouse/
syntax: rootglob
# See Profiling in rust/README.rst
.cargo/config
syntax: regexp syntax: regexp
^\.pc/ ^\.pc/
^\.(pydev)?project ^\.(pydev)?project
# hackable windows distribution additions # hackable windows distribution additions
^hg-python ^hg-python
^hg.py$ ^hg.py$

rust/README.rst

binding crates like a hypothetical ``HGWITHRUSTEXT=hpy``. binding crates like a hypothetical ``HGWITHRUSTEXT=hpy``.
Special features Special features
================ ================
You might want to check the `features` section in ``hg-cpython/Cargo.toml``. You might want to check the `features` section in ``hg-cpython/Cargo.toml``.
It may contain features that might be interesting to try out. It may contain features that might be interesting to try out.
To use features from the Makefile, use the `HG_RUST_FEATURES` environment To use features from the Makefile, use the `HG_RUST_FEATURES` environment
variable: for instance `HG_RUST_FEATURES="some-feature other-feature"` variable: for instance `HG_RUST_FEATURES="some-feature other-feature"`
Profiling Profiling
========= =========
Setting the environment variable ``RUST_LOG=trace`` will make hg print Setting the environment variable ``RUST_LOG=trace`` will make hg print
a few high level rust-related performance numbers. It can also a few high level rust-related performance numbers. It can also
indicate why the rust code cannot be used (say, using lookarounds in indicate why the rust code cannot be used (say, using lookarounds in
hgignore). 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 ``py-spy`` (https://github.com/benfred/py-spy) can be used to
construct a single profile with rust functions and python functions construct a single profile with rust functions and python functions
(as opposed to ``hg --profile``, which attributes time spent in rust (as opposed to ``hg --profile``, which attributes time spent in rust
to some unlucky python code running shortly after the rust code, and to some unlucky python code running shortly after the rust code, and
as opposed to tools for native code like ``perf``, which attribute as opposed to tools for native code like ``perf``, which attribute
time to the python interpreter instead of python functions). 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 Developing Rust
=============== ===============
The current version of Rust in use is ``1.41.1``, because it's what Debian The current version of Rust in use is ``1.41.1``, because it's what Debian
stable has. You can use ``rustup override set 1.41.1`` at the root of the repo stable has. You can use ``rustup override set 1.41.1`` at the root of the repo
to make it easier on you. to make it easier on you.
Go to the ``hg-cpython`` folder:: Go to the ``hg-cpython`` folder::