Plenty of work is being done in terms of performance improvements, and almost every release features a large set of improvements. A list of all performance related merge requests that have been merged can be found at https://gitlab.com/gitlab-org/gitlab-ce/merge_requests?scope....

If you'd like to help out you can read up on the contributing guidelines at https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBU....

Alternatively, any issues with data on what is slow and how these patterns can be reproduced is also greatly appreciated!