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1 | Git performance tests |
2 | ===================== | |
3 | ||
4 | This directory holds performance testing scripts for git tools. The | |
5 | first part of this document describes the various ways in which you | |
6 | can run them. | |
7 | ||
8 | When fixing the tools or adding enhancements, you are strongly | |
9 | encouraged to add tests in this directory to cover what you are | |
10 | trying to fix or enhance. The later part of this short document | |
11 | describes how your test scripts should be organized. | |
12 | ||
13 | ||
14 | Running Tests | |
15 | ------------- | |
16 | ||
17 | The easiest way to run tests is to say "make". This runs all | |
18 | the tests on the current git repository. | |
19 | ||
20 | === Running 2 tests in this tree === | |
21 | [...] | |
22 | Test this tree | |
23 | --------------------------------------------------------- | |
24 | 0001.1: rev-list --all 0.54(0.51+0.02) | |
25 | 0001.2: rev-list --all --objects 6.14(5.99+0.11) | |
26 | 7810.1: grep worktree, cheap regex 0.16(0.16+0.35) | |
27 | 7810.2: grep worktree, expensive regex 7.90(29.75+0.37) | |
28 | 7810.3: grep --cached, cheap regex 3.07(3.02+0.25) | |
29 | 7810.4: grep --cached, expensive regex 9.39(30.57+0.24) | |
30 | ||
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31 | Output format is in seconds "Elapsed(User + System)" |
32 | ||
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33 | You can compare multiple repositories and even git revisions with the |
34 | 'run' script: | |
35 | ||
36 | $ ./run . origin/next /path/to/git-tree p0001-rev-list.sh | |
37 | ||
38 | where . stands for the current git tree. The full invocation is | |
39 | ||
40 | ./run [<revision|directory>...] [--] [<test-script>...] | |
41 | ||
42 | A '.' argument is implied if you do not pass any other | |
43 | revisions/directories. | |
44 | ||
45 | You can also manually test this or another git build tree, and then | |
46 | call the aggregation script to summarize the results: | |
47 | ||
48 | $ ./p0001-rev-list.sh | |
49 | [...] | |
9bb81452 | 50 | $ ./run /path/to/other/git -- ./p0001-rev-list.sh |
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51 | [...] |
52 | $ ./aggregate.perl . /path/to/other/git ./p0001-rev-list.sh | |
53 | ||
54 | aggregate.perl has the same invocation as 'run', it just does not run | |
55 | anything beforehand. | |
56 | ||
57 | You can set the following variables (also in your config.mak): | |
58 | ||
59 | GIT_PERF_REPEAT_COUNT | |
60 | Number of times a test should be repeated for best-of-N | |
ca70c9ea | 61 | measurements. Defaults to 3. |
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62 | |
63 | GIT_PERF_MAKE_OPTS | |
64 | Options to use when automatically building a git tree for | |
88b6197d ÆAB |
65 | performance testing. E.g., -j6 would be useful. Passed |
66 | directly to make as "make $GIT_PERF_MAKE_OPTS". | |
67 | ||
68 | GIT_PERF_MAKE_COMMAND | |
69 | An arbitrary command that'll be run in place of the make | |
70 | command, if set the GIT_PERF_MAKE_OPTS variable is | |
71 | ignored. Useful in cases where source tree changes might | |
72 | require issuing a different make command to different | |
73 | revisions. | |
74 | ||
75 | This can be (ab)used to monkeypatch or otherwise change the | |
76 | tree about to be built. Note that the build directory can be | |
77 | re-used for subsequent runs so the make command might get | |
78 | executed multiple times on the same tree, but don't count on | |
79 | any of that, that's an implementation detail that might change | |
80 | in the future. | |
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81 | |
82 | GIT_PERF_REPO | |
83 | GIT_PERF_LARGE_REPO | |
84 | Repositories to copy for the performance tests. The normal | |
85 | repo should be at least git.git size. The large repo should | |
283efb01 | 86 | probably be about linux.git size for optimal results. |
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87 | Both default to the git.git you are running from. |
88 | ||
47274251 JK |
89 | GIT_PERF_EXTRA |
90 | Boolean to enable additional tests. Most test scripts are | |
91 | written to detect regressions between two versions of Git, and | |
92 | the output will compare timings for individual tests between | |
93 | those versions. Some scripts have additional tests which are not | |
94 | run by default, that show patterns within a single version of | |
95 | Git (e.g., performance of index-pack as the number of threads | |
96 | changes). These can be enabled with GIT_PERF_EXTRA. | |
97 | ||
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98 | You can also pass the options taken by ordinary git tests; the most |
99 | useful one is: | |
100 | ||
101 | --root=<directory>:: | |
102 | Create "trash" directories used to store all temporary data during | |
103 | testing under <directory>, instead of the t/ directory. | |
104 | Using this option with a RAM-based filesystem (such as tmpfs) | |
105 | can massively speed up the test suite. | |
106 | ||
107 | ||
108 | Naming Tests | |
109 | ------------ | |
110 | ||
111 | The performance test files are named as: | |
112 | ||
113 | pNNNN-commandname-details.sh | |
114 | ||
115 | where N is a decimal digit. The same conventions for choosing NNNN as | |
116 | for normal tests apply. | |
117 | ||
118 | ||
119 | Writing Tests | |
120 | ------------- | |
121 | ||
122 | The perf script starts much like a normal test script, except it | |
123 | sources perf-lib.sh: | |
124 | ||
125 | #!/bin/sh | |
126 | # | |
127 | # Copyright (c) 2005 Junio C Hamano | |
128 | # | |
129 | ||
130 | test_description='xxx performance test' | |
131 | . ./perf-lib.sh | |
132 | ||
133 | After that you will want to use some of the following: | |
134 | ||
91de27c5 | 135 | test_perf_fresh_repo # sets up an empty repository |
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136 | test_perf_default_repo # sets up a "normal" repository |
137 | test_perf_large_repo # sets up a "large" repository | |
138 | ||
139 | test_perf_default_repo sub # ditto, in a subdir "sub" | |
140 | ||
141 | test_checkout_worktree # if you need the worktree too | |
142 | ||
143 | At least one of the first two is required! | |
144 | ||
1a0962de JK |
145 | You can use test_expect_success as usual. In both test_expect_success |
146 | and in test_perf, running "git" points to the version that is being | |
147 | perf-tested. The $MODERN_GIT variable points to the git wrapper for the | |
148 | currently checked-out version (i.e., the one that matches the t/perf | |
149 | scripts you are running). This is useful if your setup uses commands | |
150 | that only work with newer versions of git than what you might want to | |
151 | test (but obviously your new commands must still create a state that can | |
152 | be used by the older version of git you are testing). | |
153 | ||
154 | For actual performance tests, use | |
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155 | |
156 | test_perf 'descriptive string' ' | |
157 | command1 && | |
158 | command2 | |
159 | ' | |
160 | ||
161 | test_perf spawns a subshell, for lack of better options. This means | |
162 | that | |
163 | ||
164 | * you _must_ export all variables that you need in the subshell | |
165 | ||
166 | * you _must_ flag all variables that you want to persist from the | |
167 | subshell with 'test_export': | |
168 | ||
169 | test_perf 'descriptive string' ' | |
170 | foo=$(git rev-parse HEAD) && | |
171 | test_export foo | |
172 | ' | |
173 | ||
174 | The so-exported variables are automatically marked for export in the | |
175 | shell executing the perf test. For your convenience, test_export is | |
176 | the same as export in the main shell. | |
177 | ||
178 | This feature relies on a bit of magic using 'set' and 'source'. | |
179 | While we have tried to make sure that it can cope with embedded | |
180 | whitespace and other special characters, it will not work with | |
181 | multi-line data. | |
22bec79d JK |
182 | |
183 | Rather than tracking the performance by run-time as `test_perf` does, you | |
184 | may also track output size by using `test_size`. The stdout of the | |
185 | function should be a single numeric value, which will be captured and | |
186 | shown in the aggregated output. For example: | |
187 | ||
188 | test_perf 'time foo' ' | |
189 | ./foo >foo.out | |
190 | ' | |
191 | ||
192 | test_size 'output size' | |
193 | wc -c <foo.out | |
194 | ' | |
195 | ||
196 | might produce output like: | |
197 | ||
198 | Test origin HEAD | |
199 | ------------------------------------------------------------- | |
200 | 1234.1 time foo 0.37(0.79+0.02) 0.26(0.51+0.02) -29.7% | |
201 | 1234.2 output size 4.3M 3.6M -14.7% | |
202 | ||
203 | The item being measured (and its units) is up to the test; the context | |
204 | and the test title should make it clear to the user whether bigger or | |
205 | smaller numbers are better. Unlike test_perf, the test code will only be | |
206 | run once, since output sizes tend to be more deterministic than timings. |