How can I diagnose and speed up slow Linux puppet sync?
The most direct approach is running the agent with the --evaltrace flag like
puppet agent --test --evaltrace
This will give you a good idea of which resources are the most expensive.
For your large files, you may want to experiment with different checksum alternatives.
Check : https://tickets.puppetlabs.com/browse/PA-3380 which describes slowness caused by a mix of SELinux and the number of mounts.
Nobody is picking this up, which is a shame, as most (enterprise) users will notice a speedup of at least 50%, and much less impact on system load