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Pierre-Yves David's avatar
Pierre-Yves David authored
If a revision has information overwriting data from another revision, the
overwriting revision is a descendant of the overwritten one. So we could warm
the Oracle cache with such information to avoid potential future `is_ancestors`
call.

This provide us with a large speedup in the most expensive cases:

Repo            Case                                  Source-Rev   Dest-Rev      # of revisions  old time      new time      Difference    Factor    time per rev
---------------------------------------------------------------------------------------------------------------------------------------------------------------
mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs,  41.113063 s,  36.001255 s,  -5.111808 s, × 0.8757,   157 µs/rev
mozilla-try     x00000_revs_x00000_added_x000_copies  9b2a99adc05e 8e29777b48e6 : 382065 revs,  27.891612 s,  14.340641 s, -13.550971 s, × 0.5142,    37 µs/rev




Full comparison below:

Repo            Case                                  Source-Rev   Dest-Rev      # of revisions  old time      new time      Difference    Factor    time per rev
---------------------------------------------------------------------------------------------------------------------------------------------------------------
mercurial       x_revs_x_added_0_copies               ad6b123de1c7 39cfcef4f463 :      1 revs,   0.000042 s,   0.000042 s,  +0.000000 s, × 1.0000,    42 µs/rev
mercurial       x_revs_x_added_x_copies               2b1c78674230 0c1d10351869 :      6 revs,   0.000114 s,   0.000109 s,  -0.000005 s, × 0.9561,    18 µs/rev
mercurial       x000_revs_x000_added_x_copies         81f8ff2a9bf2 dd3267698d84 :   1032 revs,   0.004934 s,   0.004953 s,  +0.000019 s, × 1.0039,     4 µs/rev
pypy            x_revs_x_added_0_copies               aed021ee8ae8 099ed31b181b :      9 revs,   0.000195 s,   0.000237 s,  +0.000042 s, × 1.2154,    26 µs/rev
pypy            x_revs_x000_added_0_copies            4aa4e1f8e19a 359343b9ac0e :      1 revs,   0.000050 s,   0.000050 s,  +0.000000 s, × 1.0000,    50 µs/rev
pypy            x_revs_x_added_x_copies               ac52eb7bbbb0 72e022663155 :      7 revs,   0.000113 s,   0.000113 s,  +0.000000 s, × 1.0000,    16 µs/rev
pypy            x_revs_x00_added_x_copies             c3b14617fbd7 ace7255d9a26 :      1 revs,   0.6f1f4a s,   0.6f1f4a s,  +0.000000 s, × 1.0000,   322 µs/rev
pypy            x_revs_x000_added_x000_copies         df6f7a526b60 a83dc6a2d56f :      6 revs,   0.010788 s,   0.010702 s,  -0.000086 s, × 0.9920,  1783 µs/rev
pypy            x000_revs_xx00_added_0_copies         89a76aede314 2f22446ff07e :   4785 revs,   0.050880 s,   0.050504 s,  -0.000376 s, × 0.9926,    10 µs/rev
pypy            x000_revs_x000_added_x_copies         8a3b5bfd266e 2c68e87c3efe :   6780 revs,   0.081760 s,   0.080159 s,  -0.001601 s, × 0.9804,    11 µs/rev
pypy            x000_revs_x000_added_x000_copies      89a76aede314 7b3dda341c84 :   5441 revs,   0.061382 s,   0.060058 s,  -0.001324 s, × 0.9784,    11 µs/rev
pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :  43645 revs,   0.585802 s,   0.536950 s,  -0.048852 s, × 0.9166,    12 µs/rev
pypy            x0000_revs_xx000_added_0_copies       bf2c629d0071 4ffed77c095c :      2 revs,   0.012803 s,   0.012868 s,  +0.000065 s, × 1.0051,  6434 µs/rev
pypy            x0000_revs_xx000_added_x000_copies    08ea3258278e d9fa043f30c0 :  11316 revs,   0.113558 s,   0.112806 s,  -0.000752 s, × 0.9934,     9 µs/rev
netbeans        x_revs_x_added_0_copies               fb0955ffcbcd a01e9239f9e7 :      2 revs,   0.000085 s,   0.000084 s,  -0.000001 s, × 0.9882,    42 µs/rev
netbeans        x_revs_x000_added_0_copies            6f360122949f 20eb231cc7d0 :      2 revs,   0.000106 s,   0.000106 s,  +0.000000 s, × 1.0000,    53 µs/rev
netbeans        x_revs_x_added_x_copies               1ada3faf6fb6 5a39d12eecf4 :      3 revs,   0.000175 s,   0.000174 s,  -0.000001 s, × 0.9943,    58 µs/rev
netbeans        x_revs_x00_added_x_copies             35be93ba1e2c 9eec5e90c05f :      9 revs,   0.000721 s,   0.000726 s,  +0.000005 s, × 1.0069,    80 µs/rev
netbeans        x000_revs_xx00_added_0_copies         eac3045b4fdd 51d4ae7f1290 :   1421 revs,   0.010127 s,   0.010105 s,  -0.000022 s, × 0.9978,     7 µs/rev
netbeans        x000_revs_x000_added_x_copies         e2063d266acd 6081d72689dc :   1533 revs,   0.015616 s,   0.015748 s,  +0.000132 s, × 1.0085,    10 µs/rev
netbeans        x000_revs_x000_added_x000_copies      ff453e9fee32 411350406ec2 :   5750 revs,   0.061341 s,   0.060357 s,  -0.000984 s, × 0.9840,    10 µs/rev
netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd :  66949 revs,   0.542214 s,   0.499356 s,  -0.042858 s, × 0.9210,     7 µs/rev
mozilla-central x_revs_x_added_0_copies               3697f962bb7b 7015fcdd43a2 :      2 revs,   0.000089 s,   0.000092 s,  +0.000003 s, × 1.0337,    46 µs/rev
mozilla-central x_revs_x000_added_0_copies            dd390860c6c9 40d0c5bed75d :      8 revs,   0.000279 s,   0.000279 s,  +0.000000 s, × 1.0000,    34 µs/rev
mozilla-central x_revs_x_added_x_copies               8d198483ae3b 14207ffc2b2f :      9 revs,   0.000184 s,   0.000186 s,  +0.000002 s, × 1.0109,    20 µs/rev
mozilla-central x_revs_x00_added_x_copies             98cbc58cc6bc 446a150332c3 :      7 revs,   0.000661 s,   0.000660 s,  -0.000001 s, × 0.9985,    94 µs/rev
mozilla-central x_revs_x000_added_x000_copies         3c684b4b8f68 0a5e72d1b479 :      3 revs,   0.003377 s,   0.003372 s,  -0.000005 s, × 0.9985,  1124 µs/rev
mozilla-central x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,   0.070508 s,   0.070294 s,  -0.000214 s, × 0.9970, 11715 µs/rev
mozilla-central x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,   0.006576 s,   0.006545 s,  -0.000031 s, × 0.9953,     4 µs/rev
mozilla-central x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,   0.004809 s,   0.004998 s,  +0.000189 s, × 1.0393,   121 µs/rev
mozilla-central x000_revs_x000_added_x000_copies      7c97034feb78 4407bd0c6330 :   7839 revs,   0.064872 s,   0.063348 s,  -0.001524 s, × 0.9765,     8 µs/rev
mozilla-central x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,   0.026142 s,   0.026154 s,  +0.000012 s, × 1.0005,    42 µs/rev
mozilla-central x0000_revs_xx000_added_x000_copies    f78c615a656c 96a38b690156 :  30263 revs,   0.203956 s,   0.199063 s,  -0.004893 s, × 0.9760,     6 µs/rev
mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 : 153721 revs,   1.763853 s,   1.277320 s,  -0.486533 s, × 0.7242,     8 µs/rev
mozilla-central x00000_revs_x00000_added_x000_copies  76caed42cf7c 1daa622bbe42 : 204976 revs,   2.609761 s,   1.698794 s,  -0.910967 s, × 0.6509,     8 µs/rev
mozilla-try     x_revs_x_added_0_copies               aaf6dde0deb8 9790f499805a :      2 revs,   0.000847 s,   0.000842 s,  -0.000005 s, × 0.9941,   421 µs/rev
mozilla-try     x_revs_x000_added_0_copies            d8d0222927b4 5bb8ce8c7450 :      2 revs,   0.000867 s,   0.000865 s,  -0.000002 s, × 0.9977,   432 µs/rev
mozilla-try     x_revs_x_added_x_copies               092fcca11bdb 936255a0384a :      4 revs,   0.000161 s,   0.000160 s,  -0.000001 s, × 0.9938,    40 µs/rev
mozilla-try     x_revs_x00_added_x_copies             b53d2fadbdb5 017afae788ec :      2 revs,   0.001131 s,   0.001122 s,  -0.000009 s, × 0.9920,   561 µs/rev
mozilla-try     x_revs_x000_added_x000_copies         20408ad61ce5 6f0ee96e21ad :      1 revs,   0.033114 s,   0.032743 s,  -0.000371 s, × 0.9888, 32743 µs/rev
mozilla-try     x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,   0.071092 s,   0.071529 s,  +0.000437 s, × 1.0061, 11921 µs/rev
mozilla-try     x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,   0.006554 s,   0.006593 s,  +0.000039 s, × 1.0060,     4 µs/rev
mozilla-try     x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,   0.005160 s,   0.005311 s,  +0.000151 s, × 1.0293,   129 µs/rev
mozilla-try     x000_revs_x000_added_x000_copies      1346fd0130e4 4c65cbdabc1f :   6657 revs,   0.065063 s,   0.063063 s,  -0.002000 s, × 0.9693,     9 µs/rev
mozilla-try     x0000_revs_x_added_0_copies           63519bfd42ee a36a2a865d92 :  40314 revs,   0.297118 s,   0.312363 s,  +0.015245 s, × 1.0513,     7 µs/rev
mozilla-try     x0000_revs_x_added_x_copies           9fe69ff0762d bcabf2a78927 :  38690 revs,   0.284002 s,   0.283106 s,  -0.000896 s, × 0.9968,     7 µs/rev
mozilla-try     x0000_revs_xx000_added_x_copies       156f6e2674f2 4d0f2c178e66 :   8598 revs,   0.086311 s,   0.083817 s,  -0.002494 s, × 0.9711,     9 µs/rev
mozilla-try     x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,   0.026738 s,   0.026516 s,  -0.000222 s, × 0.9917,    43 µs/rev
mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 :  97052 revs,   1.514270 s,   1.304865 s,  -0.209405 s, × 0.8617,    13 µs/rev
mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a :  52031 revs,   0.735875 s,   0.681088 s,  -0.054787 s, × 0.9255,    13 µs/rev
mozilla-try     x00000_revs_x_added_0_copies          6a320851d377 1ebb79acd503 : 363753 revs,   4.843329 s,   4.454320 s,  -0.389009 s, × 0.9197,    12 µs/rev
mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c :  34414 revs,   0.591752 s,   0.567913 s,  -0.023839 s, × 0.9597,    16 µs/rev
mozilla-try     x00000_revs_x_added_x_copies          5173c4b6f97c 95d83ee7242d : 362229 revs,   4.760563 s,   4.547043 s,  -0.213520 s, × 0.9551,    12 µs/rev
mozilla-try     x00000_revs_x000_added_x_copies       9126823d0e9c ca82787bb23c : 359344 revs,   4.751942 s,   4.378579 s,  -0.373363 s, × 0.9214,    12 µs/rev
mozilla-try     x00000_revs_x0000_added_x0000_copies  8d3fafa80d4b eb884023b810 : 192665 revs,   2.605014 s,   1.703622 s,  -0.901392 s, × 0.6540,     8 µs/rev
mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs,  41.113063 s,  36.001255 s,  -5.111808 s, × 0.8757,   157 µs/rev
mozilla-try     x00000_revs_x00000_added_x000_copies  9b2a99adc05e 8e29777b48e6 : 382065 revs,  27.891612 s,  14.340641 s, -13.550971 s, × 0.5142,    37 µs/rev

Differential Revision: https://phab.mercurial-scm.org/D9497
9f48fe25
History

===================
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 three independent rust projects:
- chg. An implementation of chg, in rust instead of C.
- hgcli. A project that provide 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.

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 ``1.41.1``, because it's what Debian
stable has. You can use ``rustup override set 1.41.1`` 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.