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Patrick Steinhardt 540cdc11ad pack-bitmap: avoid traversal of objects referenced by uninteresting tag When preparing the bitmap walk, we first establish the set of of have and want objects by iterating over the set of pending objects: if an object is marked as uninteresting, it's declared as an object we already have, otherwise as an object we want. These two sets are then used to compute which transitively referenced objects we need to obtain. One special case here are tag objects: when a tag is requested, we resolve it to its first not-tag object and add both resolved objects as well as the tag itself into either the have or want set. Given that the uninteresting-property always propagates to referenced objects, it is clear that if the tag is uninteresting, so are its children and vice versa. But we fail to propagate the flag, which effectively means that referenced objects will always be interesting except for the case where they have already been marked as uninteresting explicitly. This mislabeling does not impact correctness: we now have it in our "wants" set, and given that we later do an `AND NOT` of the bitmaps of "wants" and "haves" sets it is clear that the result must be the same. But we now start to needlessly traverse the tag's referenced objects in case it is uninteresting, even though we know that each referenced object will be uninteresting anyway. In the worst case, this can lead to a complete graph walk just to establish that we do not care for any object. Fix the issue by propagating the `UNINTERESTING` flag to pointees of tag objects and add a benchmark with negative revisions to p5310. This shows some nice performance benefits, tested with linux.git: Test HEAD~ HEAD --------------------------------------------------------------------------------------------------------------- 5310.3: repack to disk 193.18(181.46+16.42) 194.61(183.41+15.83) +0.7% 5310.4: simulated clone 25.93(24.88+1.05) 25.81(24.73+1.08) -0.5% 5310.5: simulated fetch 2.64(5.30+0.69) 2.59(5.16+0.65) -1.9% 5310.6: pack to file (bitmap) 58.75(57.56+6.30) 58.29(57.61+5.73) -0.8% 5310.7: rev-list (commits) 1.45(1.18+0.26) 1.46(1.22+0.24) +0.7% 5310.8: rev-list (objects) 15.35(14.22+1.13) 15.30(14.23+1.07) -0.3% 5310.9: rev-list with tag negated via --not --all (objects) 22.49(20.93+1.56) 0.11(0.09+0.01) -99.5% 5310.10: rev-list with negative tag (objects) 0.61(0.44+0.16) 0.51(0.35+0.16) -16.4% 5310.11: rev-list count with blob:none 12.15(11.19+0.96) 12.18(11.19+0.99) +0.2% 5310.12: rev-list count with blob:limit=1k 17.77(15.71+2.06) 17.75(15.63+2.12) -0.1% 5310.13: rev-list count with tree:0 1.69(1.31+0.38) 1.68(1.28+0.39) -0.6% 5310.14: simulated partial clone 20.14(19.15+0.98) 19.98(18.93+1.05) -0.8% 5310.16: clone (partial bitmap) 12.78(13.89+1.07) 12.72(13.99+1.01) -0.5% 5310.17: pack to file (partial bitmap) 42.07(45.44+2.72) 41.44(44.66+2.80) -1.5% 5310.18: rev-list with tree filter (partial bitmap) 0.44(0.29+0.15) 0.46(0.32+0.14) +4.5% While most benchmarks are probably in the range of noise, the newly added 5310.9 and 5310.10 benchmarks consistenly perform better. Signed-off-by: Patrick Steinhardt <ps@pks.im>. Signed-off-by: Junio C Hamano <gitster@pobox.com>		2021-03-22 12:10:56 -07:00
.github	Merge branch 'tb/ci-run-cocci-with-18.04' into maint	2021-02-11 13:57:36 -08:00
Documentation	Git 2.30.2	2021-02-12 15:51:13 +01:00
block-sha1	…
builtin	Merge branch 'ab/branch-sort' into maint	2021-02-08 14:05:55 -08:00
ci	ci/install-depends: attempt to fix "brew cask" stuff	2021-01-14 19:08:56 -08:00
compat	Sync with 2.29.3	2021-02-12 15:51:12 +01:00
contrib	Merge branch 'js/cmake-extra-built-ins-fix'	2020-12-14 10:21:38 -08:00
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git-gui	Merge https://github.com/prati0100/git-gui	2020-12-18 15:07:10 -08:00
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gitweb	gitweb/Makefile: conditionally include ../GIT-VERSION-FILE	2020-12-08 16:56:56 -08:00
mergetools	…
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po	l10n: zh_CN: for git v2.30.0 l10n round 1 and 2	2020-12-27 19:23:27 +08:00
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t	pack-bitmap: avoid traversal of objects referenced by uninteresting tag	2021-03-22 12:10:56 -07:00
templates	…
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CODE_OF_CONDUCT.md	…
COPYING	…
GIT-VERSION-GEN	Git 2.30.2	2021-02-12 15:51:13 +01:00
INSTALL	doc: mention Python 3.x supports	2020-12-14 15:01:03 -08:00
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Makefile	Merge branch 'js/skip-dashed-built-ins-from-config-mak' into maint	2021-02-05 16:31:28 -08:00
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apply.c	Merge branch 'ab/unreachable-break'	2020-12-18 15:15:18 -08:00
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cache.h	Sync with 2.29.3	2021-02-12 15:51:12 +01:00
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config.mak.uname	Merge branch 'rb/nonstop-config-mak-uname-update'	2020-12-18 15:15:18 -08:00
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connect.c	Merge branch 'jk/forbid-lf-in-git-url' into maint	2021-02-05 16:31:27 -08:00
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diff.c	Merge branch 'jc/diff-I-status-fix'	2020-12-18 15:15:18 -08:00
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gettext.c	gettext.c: remove/reword a mostly-useless comment	2021-01-11 13:07:33 -08:00
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git-compat-util.h	Sync with 2.29.3	2021-02-12 15:51:12 +01:00
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pack-bitmap.c	pack-bitmap: avoid traversal of objects referenced by uninteresting tag	2021-03-22 12:10:56 -07:00
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parse-options.h	parse-options: format argh like error messages	2021-01-06 15:10:27 -08:00
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patch-ids.c	Merge branch 'jk/log-cherry-pick-duplicate-patches' into maint	2021-02-05 16:31:28 -08:00
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read-cache.c	read-cache: try not to peek into `struct {lock_,temp}file`	2021-01-06 13:53:32 -08:00
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ref-filter.c	branch: show "HEAD detached" first under reverse sort	2021-01-07 15:13:21 -08:00
ref-filter.h	branch: sort detached HEAD based on a flag	2021-01-07 15:13:21 -08:00
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refs.c	init: provide useful advice about init.defaultBranch	2020-12-13 15:53:51 -08:00
refs.h	get_default_branch_name(): prepare for showing some advice	2020-12-13 15:53:50 -08:00
refspec.c	Merge branch 'fc/atmark-in-refspec'	2020-12-14 10:21:36 -08:00
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remote-curl.c	…
remote.c	Merge branch 'nk/refspecs-negative-fix'	2020-12-23 13:59:46 -08:00
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revision.c	Merge branch 'jk/log-cherry-pick-duplicate-patches' into maint	2021-02-05 16:31:28 -08:00
revision.h	…
run-command.c	Sync with 2.29.3	2021-02-12 15:51:12 +01:00
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strmap.h	strmap: make callers of strmap_remove() to call it in void context	2020-12-15 15:30:44 -08:00
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submodule.c	submodules: fix of regression on fetching of non-init subsub-repo	2020-12-09 12:32:07 -08:00
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symlinks.c	Sync with 2.20.5	2021-02-12 15:49:35 +01:00
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README.md

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