Browser page with large git repository is pretty slow since git 2.9

[Jun Omae]

After upgrading to git 2.11.1, I get speed degradation of browser page with large git repository in production environment.

The browser page calls GitNode.get_entries() for git repository. The get_entries() internally executes git log ... command at tags/trac-1.0.13/tracopt/versioncontrol/git/PyGIT.py@:914-915#L906​. However, git log ... command is pretty slow caused by detecting renames in commit.

$ time /tmp/git/2.8.4/bin/git --git-dir /path/to/git/host/reponame log --pretty=format:%n%H --name-status master -- . >/dev/null

real    0m1.596s
user    0m0.613s
sys     0m0.103s

$ time /tmp/git/2.9.3/bin/git --git-dir /path/to/git/host/reponame log --pretty=format:%n%H --name-status master -- . >/dev/null
warning: inexact rename detection was skipped due to too many files.
warning: you may want to set your diff.renameLimit variable to at least 3652 and retry the command.

real    0m42.107s
user    0m17.918s
sys     0m4.408s

Work around: adding --no-renames option to the git log ... command.

$ time /tmp/git/2.8.4/bin/git --git-dir /path/to/git/host/reponame log --pretty=format:%n%H --no-renames --name-status master -- . >/dev/null

real    0m0.288s
user    0m0.203s
sys     0m0.020s

$ time /tmp/git/2.9.3/bin/git --git-dir /path/to/git/host/reponame log --pretty=format:%n%H --no-renames --name-status master -- . >/dev/null

real    0m0.527s
user    0m0.300s
sys     0m0.044s

Large git repository:

$ du -sh /path/to/git/host/reponame
3.3G    /path/to/git/host/reponame
$ git --git-dir /path/to/git/host/reponame rev-list --all | wc -l
857

Test script:

from time import time
from trac.env import Environment

env = Environment('/path/to/trac/host/env')
from trac.versioncontrol.api import RepositoryManager
from tracopt.versioncontrol.git.git_fs import GitConnector
version = GitConnector(env)._version['v_str']
rm = RepositoryManager(env)
repos = rm.get_repository('reponame')
node = repos.get_node('/')

t = time()
try:
    list(node.get_entries())
finally:
    print('%s - %.3fs' % (version, time() - t))

Patch which unit tests pass with git 1.5.6.5 - 2.11.1:

trac/tracopt/versioncontrol/git/PyGIT.py

@@ -902 +902 @@
         base_path = self._fs_from_unicode(base_path)
 
         def name_status_gen():
-            p[:] = [self.repo.log_pipe('--pretty=format:%n%H',
+            p[:] = [self.repo.log_pipe('--pretty=format:%n%H', '--no-renames',
                                        '--name-status', sha, '--', base_path)]
             f = p[0].stdout
             for l in f:

Timing of GitNode.get_entries():

Version	w/o patch	w/ patch
1.7.4.1	0.353s	0.317s
2.3.10	0.707s	0.325s
2.4.11	0.318s	0.317s
2.5.5	0.308s	0.303s
2.7.4	0.317s	0.305s
2.8.4	0.323s	0.304s
2.9.3	46.758s	0.306s
2.10.2	47.422s	0.370s
2.11.1	49.967s	0.310s