CASSANDRA-13987 modified how the commit log sync thread works. I noticed that cql3.ViewTest and ViewBuilderTaskTest have been timing out, but only in CircleCI. When I jstack in CircleCI what I see is that the commit log writer thread is parked and the threads trying to append to the commit log are blocked waiting on it.
I tested the commit before 13987 and it passed in CircleCI and then I tested with 13987 and it timed out. I suspect this may be a general performance regression and not just a CircleCI issue.
And this is with write barriers disabled (sync thread doesn't actually sync) so it wasn't blocked in the filesystem.