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1a0962dee5
Commit 7501b59 (perf: make the tests work in worktrees,
2016-05-13) introduced the use of "git rev-parse --git-path"
in the perf-lib setup code. Because the to-be-tested version
of git is at the front of the $PATH when this code runs,
this means we cannot use modern versions of t/perf to test
versions of git older than v2.5.0 (when that option was
introduced).
This is a symptom of a more general problem. The t/perf
suite is essentially independent of git versions, and
ideally we would be able to run the most modern and complete
set of tests across many historical versions (to see how
they compare). But any setup code they run is therefore
required to use the lowest common denominator we expect to
test.
So let's introduce a new variable, $MODERN_GIT, that we can
use both in perf-lib and in the test setup to get a reliable
set of git features (we might change git and break some
tests, of course, but $MODERN_GIT is tied to the same
version of git as the t/perf scripts, so they can be fixed
or adjusted together).
This commit fixes the "--git-path" case, but does not
mass-convert existing setup code to use $MODERN_GIT. Most
setup code is fairly vanilla and will work with effectively
all versions. But now the tool is there to fix any other
issues we find going forward.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
154 lines
4.8 KiB
Text
154 lines
4.8 KiB
Text
Git performance tests
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=====================
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This directory holds performance testing scripts for git tools. The
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first part of this document describes the various ways in which you
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can run them.
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When fixing the tools or adding enhancements, you are strongly
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encouraged to add tests in this directory to cover what you are
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trying to fix or enhance. The later part of this short document
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describes how your test scripts should be organized.
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Running Tests
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-------------
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The easiest way to run tests is to say "make". This runs all
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the tests on the current git repository.
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=== Running 2 tests in this tree ===
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[...]
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Test this tree
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---------------------------------------------------------
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0001.1: rev-list --all 0.54(0.51+0.02)
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0001.2: rev-list --all --objects 6.14(5.99+0.11)
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7810.1: grep worktree, cheap regex 0.16(0.16+0.35)
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7810.2: grep worktree, expensive regex 7.90(29.75+0.37)
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7810.3: grep --cached, cheap regex 3.07(3.02+0.25)
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7810.4: grep --cached, expensive regex 9.39(30.57+0.24)
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You can compare multiple repositories and even git revisions with the
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'run' script:
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$ ./run . origin/next /path/to/git-tree p0001-rev-list.sh
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where . stands for the current git tree. The full invocation is
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./run [<revision|directory>...] [--] [<test-script>...]
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A '.' argument is implied if you do not pass any other
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revisions/directories.
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You can also manually test this or another git build tree, and then
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call the aggregation script to summarize the results:
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$ ./p0001-rev-list.sh
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[...]
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$ GIT_BUILD_DIR=/path/to/other/git ./p0001-rev-list.sh
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[...]
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$ ./aggregate.perl . /path/to/other/git ./p0001-rev-list.sh
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aggregate.perl has the same invocation as 'run', it just does not run
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anything beforehand.
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You can set the following variables (also in your config.mak):
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GIT_PERF_REPEAT_COUNT
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Number of times a test should be repeated for best-of-N
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measurements. Defaults to 3.
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GIT_PERF_MAKE_OPTS
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Options to use when automatically building a git tree for
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performance testing. E.g., -j6 would be useful.
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GIT_PERF_REPO
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GIT_PERF_LARGE_REPO
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Repositories to copy for the performance tests. The normal
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repo should be at least git.git size. The large repo should
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probably be about linux.git size for optimal results.
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Both default to the git.git you are running from.
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You can also pass the options taken by ordinary git tests; the most
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useful one is:
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--root=<directory>::
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Create "trash" directories used to store all temporary data during
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testing under <directory>, instead of the t/ directory.
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Using this option with a RAM-based filesystem (such as tmpfs)
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can massively speed up the test suite.
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Naming Tests
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------------
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The performance test files are named as:
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pNNNN-commandname-details.sh
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where N is a decimal digit. The same conventions for choosing NNNN as
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for normal tests apply.
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Writing Tests
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-------------
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The perf script starts much like a normal test script, except it
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sources perf-lib.sh:
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#!/bin/sh
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#
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# Copyright (c) 2005 Junio C Hamano
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#
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test_description='xxx performance test'
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. ./perf-lib.sh
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After that you will want to use some of the following:
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test_perf_default_repo # sets up a "normal" repository
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test_perf_large_repo # sets up a "large" repository
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test_perf_default_repo sub # ditto, in a subdir "sub"
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test_checkout_worktree # if you need the worktree too
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At least one of the first two is required!
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You can use test_expect_success as usual. In both test_expect_success
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and in test_perf, running "git" points to the version that is being
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perf-tested. The $MODERN_GIT variable points to the git wrapper for the
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currently checked-out version (i.e., the one that matches the t/perf
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scripts you are running). This is useful if your setup uses commands
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that only work with newer versions of git than what you might want to
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test (but obviously your new commands must still create a state that can
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be used by the older version of git you are testing).
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For actual performance tests, use
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test_perf 'descriptive string' '
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command1 &&
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command2
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'
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test_perf spawns a subshell, for lack of better options. This means
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that
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* you _must_ export all variables that you need in the subshell
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* you _must_ flag all variables that you want to persist from the
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subshell with 'test_export':
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test_perf 'descriptive string' '
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foo=$(git rev-parse HEAD) &&
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test_export foo
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'
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The so-exported variables are automatically marked for export in the
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shell executing the perf test. For your convenience, test_export is
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the same as export in the main shell.
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This feature relies on a bit of magic using 'set' and 'source'.
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While we have tried to make sure that it can cope with embedded
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whitespace and other special characters, it will not work with
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multi-line data.
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