PHP loads slow on nginx server

Question

I have a php application with 815k monthly unique users which loads pretty fast on my dev machine ( around 600 ms for the home page ), and used to load fast on the production server.

I am not a sysadmin, I'm just a developer, so I started to search about diagnosing the server, I followed this flowchart

Although the traffic has increased recently, the server resources seem to be fine.

%Cpu(s):  8.3 us,  2.6 sy,  0.0 ni, 87.1 id,  0.0 wa,  0.0 hi,  0.3 si,  1.7 st

I have plenty of memory available.

After narrowing down the issue, I tried something that gave me interesting results, I copied html source code from my browser and past it to test.html in the production server and it loads in less than 800ms, I take the same html code and past it test.php, and it takes around 6s to loads, both files share the same html code, no database queries are been executed in the files, So I think it has to do with something with my nginx or php configuration.

Here is my nginx configuration:

server {
    listen 80;
    server_name site-name.com;
    root /home/user/site-name.com/public;


    index index.html index.htm index.php;

    charset utf-8;

    location / {
        try_files $uri $uri/ /index.php?$query_string;
    }

    location = /favicon.ico { access_log off; log_not_found off; }
    location = /robots.txt  { access_log off; log_not_found off; }

    access_log off;
    error_log  /var/log/nginx/site-name.com-error.log error;

    error_page 404 /index.php;

    location ~ \.php$ {

        try_files $uri =404;
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
        fastcgi_index index.php;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include fastcgi_params;
    }
    location ~*  \.(jpg|jpeg|png|gif|ico|css|js|woff2)$ {
        expires 365d;
    }


    location ~ /\.ht {
        deny all;
    }
} 

css, images, html and js files load fast.

PHP fpm configuration

Solution

I found the solution, although I have server resources available, but they weren't in use, only 5 was the maximum number of child processes that was allowed to be created. I had a lot memory that wasn't being used. So I edited FPM configuration, in my case, I edited in: /etc/php/7.0/fpm/pool.d/www.conf

I did some calculation for how much memory each process use and how much I have available, and changed these values:

pm = ondemand
pm.max_children = 125
pm.start_servers =
pm.min_spare_servers = 15
pm.max_spare_servers = 25

You can check this tutorial that I followed to learn more about calculating the values.

Now it's working amazingly fast, heaviest page loads under 1s and still have enough memory.

Comments

[JayMcTee]

Next, you can consider making Nginx cache the PHP output. Especially if it's just static output, you can quite possibly microcache it, or cache it longer. That way, you can avoid a request to having to be processed by PHP because Nginx will serve it immediately from cache. Especially useful if a (slow) DB is part of the equation too.

[Kamal]

@JayMcTee Could you please link me to a reference where I can read more about it? thanks!

[Zenexer]

Sounds like you need to do some optimizing. 125 is much too high for < 1M uniques. Almost all requests should be completing in < 100ms. I also second @JayMcTee's suggestion, but that's no substitute for having speedy code. (Microcaching is pretty much a necessity at a certain point, anyway.)

[Kamal]

@Zenexer you are totally right 125 was too much high, I noticed when the memory became full in less than 24 hours, so I changed to 40.