Can you provide additional information about the system?
What are you using for disk/storage? Are you using SSD or HDD? What you you using for mounted volumes and file system?
What workloads and CI/CD pipelines are causing so many en-queued jobs?
Is this a recent issue or an ongoing problem?
You should see a significant boost in performance by upgrading to a newer version.
Updating to the latest version even provides build-in Grafana dashboards which can help in visualizing bottlenecks.
Are you running GitLab Runner on the same machine you’re running Gitlab on?
Depending on how you decide to configure GitLab Runner and what tools you use in your build hooks and pipelines, GitLab Runner can consume a significant amount of available memory. We recommend using a separate machine for GitLab Runner.
If your Runner is currently running on a separate machine, the bottleneck is likely related to IO limits of your HDD.
You can gather and share filesystem benchmarking data to investigate further.
In any case, migrating to SSD storage should improve performance significantly.
Upgrading your GitLab version should also bring some performance improvements.