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manifest: persist the manifestfulltext cache...
manifest: persist the manifestfulltext cache Reconstructing the manifest from the revlog takes time, so much so that there already is a LRU cache to avoid having to load a manifest multiple times. This patch persists that LRU cache in the .hg/cache directory, so we can re-use this cache across hg commands. Commit benchmark (run on Macos 10.13 on a 2017-model Macbook Pro with Core i7 2.9GHz and flash drive), testing without and with patch run 5 times, baseline is r2a227782e754: * committing to an existing file, against the mozilla-central repository. Baseline real time average 1.9692, with patch 1.3786. A new debugcommand "hg debugmanifestfulltextcache" lets you inspect the cache, clear it, or add specific manifest nodeids to it. When calling repo.updatecaches(), the manifest(s) for the working copy parents are added to the cache. The hg perfmanifest command has an additional --clear-disk switch to clear this cache when testing manifest loading performance. Using this command to test performance on the firefox repository for revision f947d902ed91, whose manifest has a delta chain length of 60540, we see: $ hg perfmanifest f947d902ed91 --clear-disk ! wall 0.972253 comb 0.970000 user 0.850000 sys 0.120000 (best of 10) $ hg debugmanifestfulltextcache -a `hg log --debug -r f947d902ed91 | grep manifest | cut -d: -f3` Cache contains 1 manifest entries, in order of most to least recent: id: 0294517df4aad07c70701db43bc7ff24c3ce7dbc, size 25.6 MB Total cache data size 25.6 MB, on-disk 0 bytes $ hg perfmanifest f947d902ed91 ! wall 0.036748 comb 0.040000 user 0.020000 sys 0.020000 (best of 100) Worst-case scenario: a manifest text loaded from a single delta; in the firefox repository manifest node 9a1246ff762e is the chain base for the manifest attached to revision f947d902ed91. Loading this from a full cache file is just as fast as without the cache; the extra node ids ensure a big full cache: $ for node in 9a1246ff762e 1a1922c14a3e 54a31d11a36a 0294517df4aa; do > hgd debugmanifestfulltextcache -a $node > /dev/null > done $ hgd perfmanifest -m 9a1246ff762e ! wall 0.077513 comb 0.080000 user 0.030000 sys 0.050000 (best of 100) $ hgd perfmanifest -m 9a1246ff762e --clear-disk ! wall 0.078547 comb 0.080000 user 0.070000 sys 0.010000 (best of 100)
Martijn Pieters -
r38803:0a57945a default
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Mercurial Rust Code

This directory contains various Rust code for the Mercurial project.

The top-level Cargo.toml file defines a workspace containing all primary Mercurial crates.

Building

To build the Rust components:

$ cargo build

If you prefer a non-debug / release configuration:

$ cargo build --release

Features

The following Cargo features are available:

localdev (default)

Produce files that work with an in-source-tree build.

In this mode, the build finds and uses a python2.7 binary from PATH. The hg binary assumes it runs from rust/target/<target>hg and it finds Mercurial files at dirname($0)/../../../.

Build Mechanism

The produced hg binary is bound to a CPython installation. The binary links against and loads a CPython library that is discovered at build time (by a build.rs Cargo build script). The Python standard library defined by this CPython installation is also used.

Finding the appropriate CPython installation to use is done by the python27-sys crate's build.rs. Its search order is:

  1. PYTHON_SYS_EXECUTABLE environment variable.
  2. python executable on PATH
  3. python2 executable on PATH
  4. python2.7 executable on PATH

Additional verification of the found Python will be performed by our build.rs to ensure it meets Mercurial's requirements.

Details about the build-time configured Python are built into the produced hg binary. This means that a built hg binary is only suitable for a specific, well-defined role. These roles are controlled by Cargo features (see above).

Running

The hgcli crate produces an hg binary. You can run this binary via cargo run:

$ cargo run --manifest-path hgcli/Cargo.toml

Or directly:

$ target/debug/hg
$ target/release/hg

You can also run the test harness with this binary:

$ ./run-tests.py --with-hg ../rust/target/debug/hg

Note

Integration with the test harness is still preliminary. Remember to cargo build after changes because the test harness doesn't yet automatically build Rust code.