mirror of
https://github.com/git/git.git
synced 2026-01-10 18:20:27 +00:00
87d297f483
When verifying whether refnames are available we have to verify whether
any reference exists that is nested under the current reference. E.g.
given a reference "refs/heads/foo", we must make sure that there is no
other reference "refs/heads/foo/*".
This check is performed using a ref iterator with the prefix set to the
nested reference namespace. Until now it used to not be possible to
reseek iterators, so we always had to reallocate the iterator for every
single reference we're about to check. This keeps us from reusing state
that the iterator may have and that may make it work more efficiently.
Refactor the logic to reseek iterators. This leads to a sizeable speedup
with the "reftable" backend:
Benchmark 1: update-ref: create many refs (refformat = reftable, preexisting = 100000, new = 10000, revision = HEAD~)
Time (mean ± σ): 39.8 ms ± 0.9 ms [User: 29.7 ms, System: 9.8 ms]
Range (min … max): 38.4 ms … 42.0 ms 62 runs
Benchmark 2: update-ref: create many refs (refformat = reftable, preexisting = 100000, new = 10000, revision = HEAD)
Time (mean ± σ): 31.9 ms ± 1.1 ms [User: 27.0 ms, System: 4.5 ms]
Range (min … max): 29.8 ms … 34.3 ms 74 runs
Summary
update-ref: create many refs (refformat = reftable, preexisting = 100000, new = 10000, revision = HEAD) ran
1.25 ± 0.05 times faster than update-ref: create many refs (refformat = reftable, preexisting = 100000, new = 10000, revision = HEAD~)
The "files" backend doesn't really show a huge impact:
Benchmark 1: update-ref: create many refs (refformat = files, preexisting = 100000, new = 10000, revision = HEAD~)
Time (mean ± σ): 392.3 ms ± 7.1 ms [User: 59.7 ms, System: 328.8 ms]
Range (min … max): 384.6 ms … 404.5 ms 10 runs
Benchmark 2: update-ref: create many refs (refformat = files, preexisting = 100000, new = 10000, revision = HEAD)
Time (mean ± σ): 387.7 ms ± 7.4 ms [User: 54.6 ms, System: 329.6 ms]
Range (min … max): 377.0 ms … 397.7 ms 10 runs
Summary
update-ref: create many refs (refformat = files, preexisting = 100000, new = 10000, revision = HEAD) ran
1.01 ± 0.03 times faster than update-ref: create many refs (refformat = files, preexisting = 100000, new = 10000, revision = HEAD~)
This is mostly because it is way slower to begin with because it has to
create a separate file for each new reference, so the milliseconds we
shave off by reseeking the iterator doesn't really translate into a
significant relative improvement.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
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.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-<commandname>.txt 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.txt
(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