To make it easier to track down performance problems GitLab comes with a set of profiling tools, some of these are available by default while others need to be explicitly enabled.
Sherlock is a custom profiling tool built into GitLab. Sherlock is only available when running GitLab in development mode and when setting the environment variable ENABLE_SHERLOCK to a non empty value. For example:
ENABLE_SHERLOCK=1 bundle exec rails sRecorded transactions can be found by navigating to /sherlock/transactions.
Bullet is a Gem that can be used to track down N+1 query problems. Because Bullet adds quite a bit of logging noise it's disabled by default. To enable Bullet, set the environment variable ENABLE_BULLET to a non-empty value before starting GitLab. For example:
ENABLE_BULLET=true bundle exec rails sBullet will log query problems to both the Rails log as well as the Chrome console.