accept() failed (53: Software caused connection abort)

[Adam PAPAI]

Dear List,

We've switched to Nginx because it rocks!

I have a problem with a really heavy loaded webserver:

It has 100,000,000 request per day and this number is increasing. 
(Probably 200-300M would be the peak) We are using it with php-fcgi backend.

We have 2 serious constant error messages, can be found below  [1]

[1] http://pastebin.com/6nQuEqkT

writev() failed (54: Connection reset by peer)
accept() failed (53: Software caused connection abort)

When this error occurs, the 50x page is shown OR totally disconnects and 
"could not connect to server" happens.

Our system is a:

FreeBSD iridium 8.2-RELEASE FreeBSD 8.2-RELEASE #0: Thu Feb 17 02:41:51 
UTC 2011     root at mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64

HP Proliant G7,
- 32GB memory
- CPU: Intel(R) Xeon(R) CPU  @ 2.40GHz x 6 ( x 2 ) = 24 CPU
- SAS disks

What do the error messages above mean? Has it problem with the nginx, or 
the PHP, or kernel limits? (TCP limits?)

What should I tuning? What should I set up?

The nginx relevant config parts are:


worker_processes  4;
events {
     worker_connections  4096;
}
upstream mybackend {
             server    127.0.0.1:9000;
#            server    127.0.0.1:9001;
#            server    127.0.0.1:9002;
}

     sendfile        on;
     keepalive_requests 0;


         location ~ \.php$ {
             fastcgi_pass   mybackend;
             root           html;
             include        fastcgi_params;
             fastcgi_index  index.php;
         }


Thanks in advance,


-- 
Adam PAPAI
Grapes Communication Ltd.
http://www.grapes.hu
E-mail: wooh at wooh.hu