Upgraded to gitlab-ce-10.0.3-ce.0.el6.x86_64 , web interface slow to point of timeout

After yum pulled the new version on October 6th, performance of the web interface has gone from decent to horrible - pages take up to 30 seconds to load, though assets load quickly, and checkouts work fast as ever.

The machine is configured to pull new packages nightly.

I've cleared the cache, manually vacumned and reindexed the database, reinstalled the rpm, rebuilt /etc/gitlab/gitlab.rb from scratch.

I've tried to enable the performance bar, which looks like it might give me appropriate info, but nothing in the display changes.

The only thing that has stood out is a "prometheus_multiproc_dir does not exist or is not pointing to a valid directory." message - which I was under the impression this was supposed to be automatically set up by the omnibus package.