title: GitLab 100% CPU usage by unicorn when accessing specific commit
body: <p>this is my first question here,
  so I have GitLab working on one of my server, but recently I cannot access my gitlab because of 502 error that says "Taking too much time to respond".</p>
  
  <p>I have about 50 users on my gitlab.
  When one of my users access his last two commits, unicorn starts using 100% of CPU and not allows anyone else to work, so gitlab stop working. 
  Everything else is working. Everyone can see their commits, but when accesing this one, I need to restart gitlab to make it working again.</p>
  
  <p>Gitlab is installed on partition which have 10GB of space, and <strong>only 500MB left</strong>,
  2GB of RAM, and 1 gb swap. 1vCPU(AWS instance)</p>
  
  <p>My configuration is:</p>
  
  <pre><code>  System information 
      System:         CentOS 6.7 
      Current User:   git 
      Using RVM:      no 
      Ruby Version:   2.1.8p440 
      Gem Version:    2.5.1 
      Bundler Version:1.11.2 
      Rake Version:   10.5.0 
      Sidekiq Version:4.0.1
  
      GitLab information 
      Version:        8.4.3 
      Revision:       eb6f691 
      Directory:      /opt/gitlab/embedded/service/gitlab-rails 
      DB Adapter:  postgresql 
      URL:            http://git.mydomain.lol 
      HTTP Clone URL: http://git.mydomain.lol/some-group/some-project.git 
      SSH Clone URL:  git@git.mydomain.lol:some-group/some-project.git 
      Using LDAP:     no 
      Using Omniauth: no
  
      GitLab Shell Version:        2.6.10 
  Repositories:   /projects/git-data/repositories 
  Hooks:          /opt/gitlab/embedded/service/gitlab-shell/hooks/ 
  Git:            /opt/gitlab/embedded/bin/git
  </code></pre>
  
  <p>There is nothing in logs, except in unicorn where says Unicorn killer exceeds memory limit.</p>
  
  <p>So if you need more details, please feel free to ask I will provide you anything,</p>
  
  <p>thanks for help !</p>