我有一个DigitalOcean VPS，我每月支付15美元，我正在尝试使用以下命令安装laravel envoy任务运行程序：
composer global require laravel/envoy
但是出现以下错误：
mmap() failed: [12] Cannot allocate memory
mmap() failed: [12] Cannot allocate memory
PHP Fatal error: Out of memory (allocated 459276288) (tried to allocate 2131644 bytes) in /usr/share/php/Composer/Util/RemoteFilesystem.php on line 419
Fatal error: Out of memory (allocated 459276288) (tried to allocate 2131644 bytes) in /usr/share/php/Composer/Util/RemoteFilesystem.php on line 419
有什么想法吗？