php-fpm和nginx @高CPU使用率？

我的服务器与DigitalOcean的计划如下：

2 Core Processor 2 GB Memory 

我的网站正在接受成千上万的访问者，但是，两个CPU核心都是@ 100％：

这个问题似乎与php-fpm和nginx: worker process 。 我已经对服务器做了很多优化，但是我仍然无法让它冷静下来。

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这是我的nginx.conf ：

 user www-data; worker_processes 2; pid /run/nginx.pid; events { worker_connections 2048; # multi_accept on; } http { ## # Basic Settings ## sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 65; types_hash_max_size 2048; server_tokens off; ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # server_names_hash_bucket_size 64; # server_name_in_redirect off; include /etc/nginx/mime.types; default_type application/octet-stream; ## # Logging Settings ## access_log off; error_log /var/log/nginx/error.log; ## # Gzip Settings ## gzip on; gzip_disable "msie6"; gzip_vary on; gzip_proxied expired no-cache no-store private auth; gzip_comp_level 2; gzip_min_length 1000; gzip_buffers 16 8k; gzip_http_version 1.1; gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript; ## # Buffers ## client_body_buffer_size 10K; client_header_buffer_size 1k; client_max_body_size 8m; large_client_header_buffers 2 1k; ## # nginx-naxsi config ## # Uncomment it if you installed nginx-naxsi ## #include /etc/nginx/naxsi_core.rules; ## # nginx-passenger config ## # Uncomment it if you installed nginx-passenger ## #passenger_root /usr; #passenger_ruby /usr/bin/ruby; ## # Virtual Host Configs ## include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } 

以下是我在php-fpm的www.conf启用的选项：

 user = www-data group = www-data listen = /var/run/php5-fpm.sock listen.owner = www-data listen.group = www-data pm = ondemand pm.max_children = 20 pm.start_servers = 2 pm.min_spare_servers = 1 pm.process_idle_timeout = 10s; pm.max_requests = 500 request_terminate_timeout = 20 

我如何让我的服务器超载？ 我还能改变什么？