2d59597333
These new performance tests demonstrate effectively the same behavior as
p5310, but use a multi-pack bitmap instead of a single-pack one.
Notably, p5326 does not create a MIDX bitmap with multiple packs. This
is so we can measure a direct comparison between it and p5310. Any
difference between the two is measuring just the overhead of using MIDX
bitmaps.
Here are the results of p5310 and p5326 together, measured at the same
time and on the same machine (using a Xenon W-2255 CPU):
Test HEAD
------------------------------------------------------------------------
5310.2: repack to disk 96.78(93.39+11.33)
5310.3: simulated clone 9.98(9.79+0.19)
5310.4: simulated fetch 1.75(4.26+0.19)
5310.5: pack to file (bitmap) 28.20(27.87+8.70)
5310.6: rev-list (commits) 0.41(0.36+0.05)
5310.7: rev-list (objects) 1.61(1.54+0.07)
5310.8: rev-list count with blob:none 0.25(0.21+0.04)
5310.9: rev-list count with blob:limit=1k 2.65(2.54+0.10)
5310.10: rev-list count with tree:0 0.23(0.19+0.04)
5310.11: simulated partial clone 4.34(4.21+0.12)
5310.13: clone (partial bitmap) 11.05(12.21+0.48)
5310.14: pack to file (partial bitmap) 31.25(34.22+3.70)
5310.15: rev-list with tree filter (partial bitmap) 0.26(0.22+0.04)
versus the same tests (this time using a multi-pack index):
Test HEAD
------------------------------------------------------------------------
5326.2: setup multi-pack index 78.99(75.29+11.58)
5326.3: simulated clone 11.78(11.56+0.22)
5326.4: simulated fetch 1.70(4.49+0.13)
5326.5: pack to file (bitmap) 28.02(27.72+8.76)
5326.6: rev-list (commits) 0.42(0.36+0.06)
5326.7: rev-list (objects) 1.65(1.58+0.06)
5326.8: rev-list count with blob:none 0.26(0.21+0.05)
5326.9: rev-list count with blob:limit=1k 2.97(2.86+0.10)
5326.10: rev-list count with tree:0 0.25(0.20+0.04)
5326.11: simulated partial clone 5.65(5.49+0.16)
5326.13: clone (partial bitmap) 12.22(13.43+0.38)
5326.14: pack to file (partial bitmap) 30.05(31.57+7.25)
5326.15: rev-list with tree filter (partial bitmap) 0.24(0.20+0.04)
There is slight overhead in "simulated clone", "simulated partial
clone", and "clone (partial bitmap)". Unsurprisingly, that overhead is
due to using the MIDX's reverse index to map between bit positions and
MIDX positions.
This can be reproduced by running "git repack -adb" along with "git
multi-pack-index write --bitmap" in a large-ish repository. Then run:
$ perf record -o pack.perf git -c core.multiPackIndex=false \
pack-objects --all --stdout >/dev/null </dev/null
$ perf record -o midx.perf git -c core.multiPackIndex=true \
pack-objects --all --stdout >/dev/null </dev/null
and compare the two with "perf diff -c delta -o 1 pack.perf midx.perf".
The most notable results are below (the next largest positive delta is
+0.14%):
# Event 'cycles'
#
# Baseline Delta Shared Object Symbol
# ........ ....... .................. ..........................
#
+5.86% git [.] nth_midxed_offset
+5.24% git [.] nth_midxed_pack_int_id
3.45% +0.97% git [.] offset_to_pack_pos
3.30% +0.57% git [.] pack_pos_to_offset
+0.30% git [.] pack_pos_to_midx
Signed-off-by: Taylor Blau <me@ttaylorr.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.txt to get started, then see
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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
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(man gitcvs-migration or git help cvs-migration if git is
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- 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