Re: [jgit-dev] Creating new refs on a repository with 100k packed-refs i

[kaushikl@xxxxxxxxxxxxxx]

On 2020-10-06 12:16, kaushikl@xxxxxxxxxxxxxx wrote:
> Hi,
>
> We have noticed that creating a new ref takes ~600ms on a repository
> with around 100k packed-refs.
>
> My test repository:
>
>     $ git count-objects -v
>     count: 0
>     size: 0
>     in-pack: 100042
>     packs: 1
>     size-pack: 9734
>     prune-packable: 0
>     garbage: 0
>     size-garbage: 0
>
>     $ find refs/ -type f | wc -l
>     0
>
> Specs:
>
>     Machine has 32 cores and 250G RAM.
>
>     $ uname -r
>     4.4.0-165-generic
>
>     $ lsb_release -a
>     No LSB modules are available.
>     Distributor ID:    Ubuntu
>     Description:    Ubuntu 16.04.6 LTS
>     Release:    16.04
>     Codename:    xenial
>
>     Jgit version is 5.9
>
>     $ java -version
>     openjdk version "1.8.0_242"
>     OpenJDK Runtime Environment (build 
> 1.8.0_242-8u242-b08-0ubuntu3~16.04-b08)
>     OpenJDK 64-Bit Server VM (build 25.242-b08, mixed mode)
>
> Consider a small program[1] which creates a ref 'simple'. On executing
> the program on my test repository, I see output:
>
> simple: 677 ms
>
> This seems slow. Is this expected behavior with jgit?

Adding repo-discuss@xxxxxxxxxxxxxxxx to Cc as this seems to be affecting 
notedb migration times of large projects.

> [1]
> package test;
>
> import java.io.File;
> import java.io.IOException;
> 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);
>       }
>       String branch = "simple";
>       try (Git git = Git.open(new File(path))) {
>         Repository repo = git.getRepository();
>         RevWalk walk = new RevWalk(repo);
>         RevCommit commit =
> walk.parseCommit(repo.exactRef("refs/heads/master").getObjectId());
>         long startTimeInNanoSecs = System.nanoTime();
>         
> git.branchCreate().setName(branch).setStartPoint(commit).call();
>         long estimatedTimeInNanoSecs = System.nanoTime() - 
> startTimeInNanoSecs;
>         System.out.println(branch + ": " +
> TimeUnit.NANOSECONDS.toMillis(estimatedTimeInNanoSecs) + " ms");
>       }
>     } catch (IllegalStateException | GitAPIException | IOException e) {
>       e.printStackTrace();
>     }
>   }
> }
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