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Re: [jgit-dev] Refs creation slowness with Jgit
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CC: repo-discuss@xxxxxxxxxxxxxxxx
On 2020-09-23 09:13, kaushikl@xxxxxxxxxxxxxx wrote:
Hello,
When investigating slow Gerrit NoteDB migration times, we noticed a
slowness with jgit creating refs. During the migration a ref is
created for each Gerrit change, for example ‘changes/01/1/meta’,
‘changes/02/2/meta’, ‘changes/03/3/meta’ and so on. We see the
slowness when creating refs in a new path. This behaviour is
repeatable, i.e each time a ref is created in a new path, it is slow.
We noticed it is fast on some machines, but we couldn't quite nail
down why.
I have a small sample program[1] which illustrates the slowness. It
creates two refs 'refs/heads/test_simple' and 'refs/heads/test/foo'.
On executing the program, I see output:
test/foo: 325 ms
test_simple: 4 ms
My expectation is that 'test/foo' will also be created in order of
milliseconds and not in order of few hundred milliseconds. The
slowness seems to be stemming from the Files.getFileStore(dir) call in
FS.FileStoreAttributes.getFileStoreAttributes(Path dir).
Specs:
Jgit version is 5.9
$ java -version # also tried with version 1.8.0_252
openjdk version "1.8.0_232"
OpenJDK Runtime Environment (build
1.8.0_232-8u232-b09-0ubuntu1~16.04.1-b09)
OpenJDK 64-Bit Server VM (build 25.232-b09, mixed mode)
$ uname -r
4.15.0-54-generic
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.6 LTS
Release: 16.04
Codename: xenial
Filesystem type is ext4
[1]
package test;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
public class Test {
public static void main(String[] args) {
try {
String path = null;
if (args.length == 1) {
path = args[0];
} else {
System.out.println("Repo path must be specified.");
System.exit(1);
}
Path repoPath = Paths.get(path);
long startTimeInNanoSecs;
long estimatedTimeInNanoSecs;
Git git = Git.init().setDirectory(repoPath.toFile()).call();
Repository repo = git.getRepository();
RevWalk walk = new RevWalk(repo);
Files.write(repoPath.resolve("file"), Arrays.asList("line"),
StandardCharsets.UTF_8);
git.add().addFilepattern("file").call();
git.commit().setMessage("create file").setAuthor("author",
"author@xxxxxxxxx").call();
RevCommit commit =
walk.parseCommit(repo.exactRef("refs/heads/master").getObjectId());
String branch = "test/foo";
startTimeInNanoSecs = System.nanoTime();
git.branchCreate().setName(branch).setStartPoint(commit).call();
estimatedTimeInNanoSecs = System.nanoTime() -
startTimeInNanoSecs;
System.out.println(branch + ": " +
TimeUnit.NANOSECONDS.toMillis(estimatedTimeInNanoSecs) + " ms");
branch = "test_simple";
startTimeInNanoSecs = System.nanoTime();
git.branchCreate().setName(branch).setStartPoint(commit).call();
estimatedTimeInNanoSecs = System.nanoTime() -
startTimeInNanoSecs;
System.out.println(branch + ": " +
TimeUnit.NANOSECONDS.toMillis(estimatedTimeInNanoSecs) + " ms");
} catch (IllegalStateException | GitAPIException | IOException e) {
e.printStackTrace();
}
}
}
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