"If your OS supports sharing of memory (and most sane systems
do), you might save a lot of RAM by sharing it between child
processes. This will allow you to run more processes and hopefully
better satisfy the client, without investing extra money into
buying more memory."
"... The ideal is a point where your processes usually
restart before too much memory becomes unshared. You should take
some measurements to see if it makes a real difference, and to find
the range of reasonable values. If you have success with this
tuning the value of MaxRequestsPerChild will probably be peculiar
to your situation and may change with changing circumstances."