Apache Reference: http_core, RLimitMEM

RLimitMEM

Resource Limit on Memory Usage
Syntax: RLimitMEM soft-bytes [hard-bytes]
Example: RLimitMEM 1048576 2097152
Since: Apache 1.2

This directive sets the soft and hard limits for maximum memory usage of a process in bytes. It takes one or two parameters. The first parameter sets the soft resource limit for all processes. The second parameter sets the maximum resource limit. Either parameter can be a number, or ``max'', which indicates to the server that the limit should match the maximum allowed by the operating system configuration. Raising the maximum resource limit requires the server to be running as the user ``root'' or in the initial start-up phase.