You can set memory usage limits on a vhost basis.
I can't remember the exact command but it is something really simple - a one liner in httpd.conf
Edit:
Found it....
RLimitCPU[/url] Directive[/url]
Description: Limits the CPU consumption of processes launched by Apache children
Syntax: RLimitCPU number|max [number|max]
Default: Unset; uses operating system defaults
Context: server config, virtual host, directory, .htaccess
Override: All
Status: Core
Module: core
Takes 1 or 2 parameters. The first parameter sets the soft resource limit for all processes and the second parameter sets the maximum resource limit. Either parameter can be a number, or max to indicate to the server that the limit should be set to the maximum allowed by the operating system configuration. Raising the maximum resource limit requires that the server is running as root, or in the initial startup phase.
This applies to processes forked off from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache parent such as piped logs.
CPU resource limits are expressed in seconds per process. See also
RLimitMEM[/url] Directive[/url]
Description: Limits the memory consumption of processes launched by Apache children
Syntax: RLimitMEM number|max [number|max]
Default: Unset; uses operating system defaults
Context: server config, virtual host, directory, .htaccess
Override: All
Status: Core
Module: core
Takes 1 or 2 parameters. The first parameter sets the soft resource limit for all processes and the second parameter sets the maximum resource limit. Either parameter can be a number, or max to indicate to the server that the limit should be set to the maximum allowed by the operating system configuration. Raising the maximum resource limit requires that the server is running as root, or in the initial startup phase.
This applies to processes forked off from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache parent such as piped logs.
Memory resource limits are expressed in bytes per process. See also
RLimitNPROC[/url] Directive[/url]
Description: Limits the number of processes that can be launched by processes launched by Apache children
Syntax: RLimitNPROC number|max [number|max]
Default: Unset; uses operating system defaults
Context: server config, virtual host, directory, .htaccess
Override: All
Status: Core
Module: core
Takes 1 or 2 parameters. The first parameter sets the soft resource limit for all processes and the second parameter sets the maximum resource limit. Either parameter can be a number, or max to indicate to the server that the limit should be set to the maximum allowed by the operating system configuration. Raising the maximum resource limit requires that the server is running as root, or in the initial startup phase.
This applies to processes forked off from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache parent such as piped logs.
Process limits control the number of processes per user.
Note: If CGI processes are
not running under userids other than the web server userid, this directive will limit the number of processes that the server itself can create. Evidence of this situation will be indicated by
cannot fork messages in the error_log. See also
