| commit | 89a1ab8fb5766d0474ff72f176804508b0558f8a | [log] [tgz] |
|---|---|---|
| author | Derrick Stolee <derrickstolee@github.com> | Mon Sep 26 13:17:57 2022 +0000 |
| committer | Junio C Hamano <gitster@pobox.com> | Mon Sep 26 12:09:18 2022 -0700 |
| tree | b82b6401f81836a796464e49a11f6cd15aa806d5 | |
| parent | 969a5645876ccf368ed74fde2c5dc9b5432b7bb0 [diff] |
pack-bitmap: remove trace2 region from hot path The trace2 region around the call to lazy_bitmap_for_commit() in bitmap_for_commit() was added in 28cd730680d (pack-bitmap: prepare to read lookup table extension, 2022-08-14). While adding trace2 regions is typically helpful for tracking performance, this method is called possibly thousands of times as a commit walk explores commit history looking for a matching bitmap. When trace2 output is enabled, this region is emitted many times and performance is throttled by that output. For now, remove these regions entirely. This is a critical path, and it would be valuable to measure that the time spent in bitmap_for_commit() does not increase when using the commit lookup table. The best way to do that would be to use a mechanism that sums the time spent in a region and reports a single value at the end of the process. This technique was introduced but not merged by [1] so maybe this example presents some justification to revisit that approach. [1] https://lore.kernel.org/git/pull.1099.v2.git.1640720202.gitgitgadget@gmail.com/ To help with the 'git blame' output in this region, add a comment that warns against adding a trace2 region. Delete a test from t5310 that used that trace output to check that this lookup optimization was activated. To create this kind of test again in the future, the stopwatch traces mentioned earlier could be used as a signal that we activated this code path. Helpedy-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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 with just “subscribe git” in the body to majordomo@vger.kernel.org (not the Git list). The mailing list archives are available at https://lore.kernel.org/git/, http://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):