Master Nginx Performance: Worker Processes, CPU Affinity, and Tuning Guide

1. Nginx Worker Processes

Nginx typically sets worker_processes to the number of CPU cores or cores × 2. You can discover the core count with top -1 or grep ^processor /proc/cpuinfo | wc -l.

worker_processes 4;

2. Nginx CPU Affinity

Bind each worker to a specific CPU core to improve cache locality.

worker_processes 4;
worker_cpu_affinity 0001 0010 0100 1000;

For an 8‑core server:

worker_processes 8;
worker_cpu_affinity 00000001 00000010 00000100 00001000 00010000 00100000 01000000 10000000;

More than eight workers rarely improve performance and may reduce stability.

3. Maximum Open Files

worker_rlimit_nofile 65535;

This directive should match the system ulimit -n value; otherwise Nginx may run out of file descriptors.

4. Event Handling Model

events {
    use epoll;
    worker_connections 65535;
    multi_accept on;
}

Using epoll provides high efficiency. worker_connections defines the maximum connections per worker; the total possible connections equal worker_processes × worker_connections. multi_accept controls whether a worker accepts as many pending connections as possible after a notification.

5. Efficient File Transfer

http {
    include mime.types;
    default_type application/octet-stream;
    sendfile on;
    tcp_nopush on;
}

sendfile

enables zero‑copy file transmission; tcp_nopush reduces packet fragmentation when sendfile is on.

6. Connection Timeout Settings

keepalive_timeout 60;
 tcp_nodelay on;
 client_header_buffer_size 4k;
 open_file_cache max=102400 inactive=20s;
 open_file_cache_valid 30s;
 open_file_cache_min_uses 1;
 client_header_timeout 15;
 client_body_timeout 15;
 reset_timedout_connection on;
 send_timeout 15;
 server_tokens off;
 client_max_body_size 10m;

These directives protect server resources, control idle connections, and fine‑tune caching of opened files.

7. FastCGI Tuning

fastcgi_connect_timeout 600;
fastcgi_send_timeout 600;
fastcgi_read_timeout 600;
fastcgi_buffer_size 64k;
fastcgi_buffers 4 64k;
fastcgi_busy_buffers_size 128k;
fastcgi_temp_file_write_size 128k;
fastcgi_temp_path /usr/local/nginx1.10/nginx_tmp;
fastcgi_intercept_errors on;
fastcgi_cache_path /usr/local/nginx1.10/fastcgi_cache levels=1:2 keys_zone=cache_fastcgi:128m inactive=1d max_size=10g;
fastcgi_cache_key http://$host$request_uri;
fastcgi_cache_valid 200 302 1h;
fastcgi_cache_valid 301 1d;
fastcgi_cache_valid any 1m;
fastcgi_cache_min_uses 1;
fastcgi_pass 127.0.0.1:9000;

Proper buffer sizes and cache settings reduce CPU load and prevent 502 errors.

8. Gzip Compression

gzip on;
 gzip_min_length 2k;
 gzip_buffers 4 32k;
 gzip_http_version 1.1;
 gzip_comp_level 6;
 gzip_types text/plain text/css text/javascript application/json application/javascript application/xml;
 gzip_vary on;
 gzip_proxied any;

Gzip saves bandwidth but consumes CPU; compress only text‑based assets.

9. Expires Caching

Cache static assets to reduce bandwidth and improve user experience.

location ~* \.(ico|jpe?g|gif|png|bmp|swf|flv)$ {
    expires 30d;
    access_log off;
}
location ~* \.(js|css)$ {
    expires 7d;
    access_log off;
}

10. Anti‑Hotlinking

location ~* \.(jpg|gif|png|swf|flv|wma|wmv|asf|mp3|mmf|zip|rar)$ {
    valid_referers none blocked www.example.com example.com;
    if ($invalid_referer) {
        return 404;
    }
    access_log off;
}

11. Kernel Parameter Optimization

fs.file-max = 999999
net.ipv4.tcp_max_tw_buckets = 6000
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_keepalive_time = 30
net.ipv4.tcp_syncookies = 1
net.core.somaxconn = 40960
net.core.netdev_max_backlog = 262144
net.ipv4.tcp_max_syn_backlog = 262144
net.ipv4.tcp_rmem = 10240 87380 12582912
net.ipv4.tcp_wmem = 10240 87380 12582912
net.core.rmem_default = 6291456
net.core.wmem_default = 6291456
net.core.rmem_max = 12582912
net.core.wmem_max = 12582912

Apply with sysctl -p.

12. System Open Files Limit

Default ulimit -n is 1024, which is insufficient for high‑traffic servers.

# Increase limits in /etc/security/limits.conf
* soft nofile 65535
* hard nofile 65535
* soft noproc 65535
* hard noproc 65535

After editing, re‑login or restart services for the new limits to take effect.