我的主题有误。服务器负载不高：大约15％的CPU，有几个Gb的内存，HDD并不忙。但是错误502大约会引发3％的情况。

程序：Debian 6，nginx / 0.7.62，php5-fpm（5.3.3-1）。

在nginx的error.log中是此错误：

connect() to unix:/var/run/php5-fpm.sock failed

php5-fpm的状态通常是这样的：

accepted conn:   41680
pool:             www
process manager:  dynamic
idle processes:   258
active processes: 1
total processes:  259

我认为，这意味着负载不高。

我增加了积压参数：在sysctl中-net.core.somaxconn = 5000，在php-fpm池中-listen.backlog
=5000。没有效果。

我引用一个配置：

/etc/nginx/nginx.conf

user www-data;
worker_processes  8;
timer_resolution 100ms;
worker_rlimit_nofile 20240;
worker_priority -5;

error_log  /var/log/nginx/error.log;
pid        /var/run/nginx.pid;

events {
    worker_connections  2048;
    use epoll;
    # multi_accept on;
}

http {
    include       /etc/nginx/mime.types;

    access_log  /var/log/nginx/access.log;

    sendfile        on;
    tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;
    tcp_nodelay        on;

    gzip  on;
    gzip_min_length 1100;
    gzip_buffers 64 8k;
    gzip_comp_level 3;
    gzip_http_version 1.1;
    gzip_proxied any;
    gzip_types text/plain application/xml application/x-javascript text/css;
    gzip_disable "MSIE [1-6]\.(?!.*SV1)";

    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;

    client_max_body_size 100M;
    server_tokens off;
}

/ etc / nginx / php_location

fastcgi_pass   unix:/var/run/php5-fpm.sock;
fastcgi_index  index.php;
fastcgi_param  SCRIPT_FILENAME  $document_root/$fastcgi_script_name;
fastcgi_buffers 256 128k;
#fastcgi_buffer_size 16k;
#fastcgi_busy_buffers_size 256k;
fastcgi_connect_timeout 300s;
fastcgi_send_timeout 300s;
fastcgi_read_timeout 300s;
include fastcgi_params;

php-fpm池

[www]
listen = /var/run/php5-fpm.sock
listen.backlog = 5000
listen.owner = www-data
listen.group = www-data
listen.mode = 0666
user = www-data
group = www-data
pm = dynamic
pm.max_children = 1024
pm.start_servers = 64
pm.min_spare_servers = 64
pm.max_spare_servers = 128
pm.max_requests = 32000
pm.status_path = /system/php5-fpm-status
slowlog = /var/www/log/php-fpm.log.slow
chdir = /var/www

如何优化该系统并使之使用所有服务器资源？

PS。对不起，我的英语不好。