The apache documentation states a DNS lookup will be performed when the Allow from (or Deny from) clause contains a domain name (e.g Allow from myserver.com). What if the domain name and IP is listed /etc/hosts?
Apache use nsswitch. If IP address in /etc/hosts then use /etc/hosts information.
Comment "10.0.2.15 localhost" in /etc/hosts:
Uncomment "10.0.2.15 localhost" in /etc/hosts:
but performance still decreases: