Pillar:

apache:
  default: bellingham
  options:
    minspareservers: 20
    maxspareservers: 30
    maxclients: 60
    keepalive: 'Off'


State:

/etc/apache2/apache2.conf:
  file:
    - managed
    - source: salt://apache/apache2.conf
    - template: jinja
    - defaults:
        minspareservers: 5
        maxspareservers: 10
        maxclients: {{ ((grains.mem_total - 300) / 90) | int }}
        keepalivetimeout: 0
        keepalive: "Off"
    {% if salt['pillar.get']('apache:options', False) %}
    - context:
        minspareservers: {{ salt['pillar.get']('apache:options:minspareservers', 5) }}
        maxspareservers: {{ salt['pillar.get']('apache:options:maxspareservers', 10) }}
        maxclients: {{ salt['pillar.get']('apache:options:maxclients', ((grains.mem_total-500)/90) | int ) }}
        keepalivetimeout: {{ salt['pillar.get']('apache:options:keepalivetimeout', 0) }}
        keepalive: {{ salt['pillar.get']('apache:options:keepalive', "Off") }}
    {% endif %}


apache2.conf:

#
# KeepAlive: Whether or not to allow persistent connections (more than
# one request per connection). Set to "Off" to deactivate.
#
KeepAlive {{ keepalive }}