Noticed it exceeded 512MB, then 2GB, ...
It was running in an endless loop because
PHP Fatal error: Uncaught ArgumentCountError: Too few arguments to function Zend_Session_Exception::handleSessionStartError(), 4 passed and exactly 5 expected i
See https://www.php.net/manual/en/function.set-error-handler.php
Since PHP 8: errcontext was removed, and will no longer be passed to user callbacks.
There might be also other places where we maybe use error handler