Comment 4 for bug 1690756

I was able to follow up with Morgan about this in IRC [0]. It sounds like our sizing would be the following

- Use oslo_cache.memcache_pool for environments running 100 threads or more
- Use dogpile.cache.memcached for environments running less than 100 threads but more than a single thread
- Use dogpile.cache.memory for environments isolated to a single process or thread of execution.

This could be accompanied with a statement of tuning like Morgan suggests in IRC. If folks think this is an improvement, I'll get a patch proposed to oslo.cache.

[0] http://eavesdrop.openstack.org/irclogs/%23openstack-keystone/%23openstack-keystone.2017-05-17.log.html#t2017-05-17T14:21:19