There is a major deficiency in parts of EM code that makes the operations slower. We need to profile and introduce lookup structures to speed up read/write ops in EM. ExtentMap::getDbRootHWMInfo() must be overloaded to serve multiple oids at a time. ExtentMap::setLocalHWM is called multiple times compacting journal into EM on MCS shutdown(save_brm presumably). setLocalHWM is utterly slow that forces systemd to kill save_brm on timeout.