Percona MongoDB InMemory performance tuning

Hello everyone,I’m looking for battle tested tips for tuning MongoDB and OS in order to achieve better throughput and latency.

For that broad topic I would suggest by Vinnie Grippa as a first stop.
If you’re definitely going to use only the In-memory engine, well, anything to do with filesystems will be beside the point as the data files won’t be on disk. Also when using in-memory you can make the WiredTiger cache most of the RAM; with normal use you should leave a large proportion of RAM to be available for the OS’s filecache.