nginx报错104: Connection reset by peer

错误提示：recv() failed (104: Connection reset by peer) while reading response header from upstream
按照网上的办法操作过还是如此：
linux 2核 4G内存
php-fpm:
pm.max_requests = 500
request_terminate_timeout = 0
pm.max_children = 100
php.ini
memory_limit = 128M
max_execution_time = 60
重启php还是报错