"Cannot allocate memory: couldn't spawn child process" error in Apache logs with Cloudlinux

The following error indicates that the Apache service was unable to reserve memory for the new child process. 

(12)Cannot allocate memory: [client {IP}:{PORT}] couldn't create child process: 12: ea-php{VERSION}

Affected page requests will commonly return a 500 error response. This error is often the result of the server running out of available memory or when LVE limits are preventing allocation. To address this, you will first need to determine which of the following is the cause. 

While the error is occurring, you will want to check to confirm that your system is not running low or out of available memory. You can check your system's available memory in the interface Server Information(WHM »Home »Server Status »Server Information) under the section labeled "Current Memory Usage". If this is the cause, you will need to reduce usage or increase the available memory on the system.

When a cPanel user exceeds the PMEM limit in the LVE settings they will be restricted from allocating more memory to their processes. You can view the recent limit faults in the LVE Manager interface(WHM »Home »Server Configuration »CloudLinux LVE Manager). The statistics tab can be used to check for current or historical faults. This can determine if a user has reached their PMEM setting. If the account is reaching this limit, the memory usage will need to be reduced or the limit can be increased. 

This error can also occur if there is a limit configured for the VMEM setting. This value should always be set to 0 as it was deprecated by Cloudlinux and can result in abnormal behavior. For additional information regarding this, see the Cloudlinux article below. 

https://docs.cloudlinux.com/limits/