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Adapting the implementation of ll_find_deltas(), create a threaded version of the --path-walk compression step in 'git pack-objects'. This involves adding a 'regions' member to the thread_params struct, allowing each thread to own a section of paths. We can simplify the way jobs are split because there is no value in extending the batch based on name-hash the way sections of the object entry array are attempted to be grouped. We re-use the 'list_size' and 'remaining' items for the purpose of borrowing work in progress from other "victim" threads when a thread has finished its batch of work more quickly. Using the Git repository as a test repo, the p5313 performance test shows that the resulting size of the repo is the same, but the threaded implementation gives gains of varying degrees depending on the number of objects being packed. (This was tested on a 16-core machine.) Test HEAD~1 HEAD --------------------------------------------------- 5313.20: big pack 2.38 1.99 -16.4% 5313.21: big pack size 16.1M 16.0M -0.2% 5313.24: repack 107.32 45.41 -57.7% 5313.25: repack size 213.3M 213.2M -0.0% (Test output is formatted to better fit in message.) This ~60% reduction in 'git repack --path-walk' time is typical across all repos I used for testing. What is interesting is to compare when the overall time improves enough to outperform the --name-hash-version=1 case. These time improvements correlate with repositories with data shapes that significantly improve their data size as well. The --path-walk feature frequently takes longer than --name-hash-version=2, trading some extra computation for some additional compression. The natural place where this additional computation comes from is the two compression passes that --path-walk takes, though the first pass is naturally faster due to the path boundaries avoiding a number of delta compression attempts. For example, the microsoft/fluentui repo has significant size reduction from --name-hash-version=1 to --name-hash-version=2 followed by further improvements with --path-walk. The threaded computation makes --path-walk more competitive in time compared to --name-hash-version=2, though still ~31% more expensive in that metric. Repack Method Pack Size Time ------------------------------------------ Hash v1 439.4M 87.24s Hash v2 161.7M 21.51s Path Walk (Before) 142.5M 81.29s Path Walk (After) 142.5M 28.16s Similar results hold for the Git repository: Repack Method Pack Size Time ------------------------------------------ Hash v1 248.8M 30.44s Hash v2 249.0M 30.15s Path Walk (Before) 213.2M 142.50s Path Walk (After) 213.3M 45.41s ...as well as the nodejs/node repository: Repack Method Pack Size Time ------------------------------------------ Hash v1 739.9M 71.18s Hash v2 764.6M 67.82s Path Walk (Before) 698.1M 208.10s Path Walk (After) 698.0M 75.10s Finally, the Linux kernel repository is a good test for this repacking time change, even though the space savings is more subtle: Repack Method Pack Size Time ------------------------------------------ Hash v1 2.5G 554.41s Hash v2 2.5G 549.62s Path Walk (before) 2.2G 1562.36s Path Walk (before) 2.2G 559.00s Signed-off-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.adoc to get started, then see
Documentation/giteveryday.adoc for a useful minimum set of commands, and
Documentation/git-<commandname>.adoc for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.adoc
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
To subscribe to the list, send an email to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://marc.info/?l=git and other archival sites.
Issues which are security relevant should be disclosed privately to the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks