bf972896d7
When "cat-file --batch-all-objects" iterates over each object, it knows where to find each one. But when we look up details of the object, we don't use that information at all. This patch teaches it to use the pack/offset pair when we're iterating over objects in a pack. This yields a measurable speed improvement (timings on a fully packed clone of linux.git): Benchmark #1: ./git.old cat-file --batch-all-objects --unordered --batch-check="%(objecttype) %(objectname)" Time (mean ± σ): 8.128 s ± 0.118 s [User: 7.968 s, System: 0.156 s] Range (min … max): 8.007 s … 8.301 s 10 runs Benchmark #2: ./git.new cat-file --batch-all-objects --unordered --batch-check="%(objecttype) %(objectname)" Time (mean ± σ): 4.294 s ± 0.064 s [User: 4.167 s, System: 0.125 s] Range (min … max): 4.227 s … 4.457 s 10 runs Summary './git.new cat-file --batch-all-objects --unordered --batch-check="%(objecttype) %(objectname)"' ran 1.89 ± 0.04 times faster than './git.old cat-file --batch-all-objects --unordered --batch-check="%(objecttype) %(objectname)" The implementation is pretty simple: we just call packed_object_info() instead of oid_object_info_extended() when we can. Most of the changes are just plumbing the pack/offset pair through the callstack. There is one subtlety: replace lookups are not handled by packed_object_info(). But since those are disabled for --batch-all-objects, and since we'll only have pack info when that option is in effect, we don't have to worry about that. There are a few limitations to this optimization which we could address with further work: - I didn't bother recording when we found an object loose. Technically this could save us doing a fruitless lookup in the pack index. But opening and mmap-ing a loose object is so expensive in the first place that this doesn't matter much. And if your repository is large enough to care about per-object performance, most objects are going to be packed anyway. - This works only in --unordered mode. For the sorted mode, we'd have to record the pack/offset pair as part of our oid-collection. That's more code, plus at least 16 extra bytes of heap per object. It would probably still be a net win in runtime, but we'd need to measure. - For --batch, this still helps us with getting the object metadata, but we still do a from-scratch lookup for the object contents. This probably doesn't matter that much, because the lookup cost will be much smaller relative to the cost of actually unpacking and printing the objects. For small objects, we could probably swap out read_object_file() for using packed_object_info() with a "object_info.contentp" to get the contents. But we'd still need to deal with streaming for larger objects. A better path forward here is to teach the initial oid_object_info_extended() / packed_object_info() calls to retrieve the contents of smaller objects while they are already being accessed. That would save the extra lookup entirely. But it's a non-trivial feature to add to the object_info code, so I left it for now. Signed-off-by: Jeff King <peff@peff.net> 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). To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org. 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):
- 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