The update fuzzer runs at up to 15x slower on the 3.6 branch compare with master. This is especially pronounced in the OS X and Code Coverage variants. (Enterprise OS X MMAP1, SSL OS X, RHEL 6.2 DEBUG Code Coverage), causing timeouts in the update_fuzzer_replication suite on these variants. The other variants all suffer between a 2x to 5x slowdown, but not enough to trigger a timeout.

The slowdown is likely caused by the additional work of resetting the database and running more JavaScript in the shell to handle blacklisting. 3.7 has not had a similar problem so far, but it should experience a similar slowdown as more known differences are discovered between 3.7 and 3.6.

It might be a good idea to proactively reduce the number of fuzzer generated files and the size of each file to prevent sporadic failures in the future, especially for the update_fuzzer_replication suite.