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FcgidMaxProcesses -- this is the total number of processes FCGID will start, for all users. That is what will prevent OOM issues. The more RAM you have, the higher you can set the value. If you set this value too low, you will get 500 errors, as FCGID will not be able to create new processes to serve requests. This value also depends on the size of PHP processes (which in turn depends on extensions that you have enabled for PHP) as the larger the process the faster you will him OOM. You can try playing with following numbers depending on your RAM: 8GB -- about 150, 16GB – 300 Also, make sure you monitor apache error logs. If you see "can't apply process slot for error" -- it means you are hitting FcgidMaxProcesses
Tente aumentar o FcgidMaxProcesses para 150