Simple threading question

[Igor Sysoev]

On Sun, Sep 26, 2010 at 11:05:00PM -0700, Ankur Gupta wrote:

> Hi,
> 
> I have a bunch of nginx and php-fpm worker threads.  I am running a
> very simple test with a script doing: <? sleep(20); ?>.  I notice that
> if I make two requests at the same time (from the same IP address), they get
> serialized on the
> php-fpm side and have a twenty second differential.  Why would this
> happen and the two requests not get processed in parallel when there
> are an abundant number of threads?  Here are the two requests in the
> slow log file and they have a twenty second difference:
> 
> Sep 26 19:02:38.177091 pid 13597 (pool default)
> script_filename = /var/www/test1/test.php
> [0x00000000095b5280] sleep() /var/www/test1/test.php:2
> 
> Sep 26 19:02:58.321560 pid 13609 (pool default)
> script_filename = /var/www/test1/test.php
> [0x000000000942a890] sleep() /var/www/test1/test.php:2
> 
> I have 100+ nginx threads
> $ ps -afe | grep nginx | wc -l
> 120
> 
> and 150 php-fpm threads
> $ ps -afe | grep php-fpm | wc -l
> 150

nginx does not serialize requests to FastCGI. A single nginx worker can
handle tens thousand concurrent FastCGI connections.


-- 
Igor Sysoev
http://sysoev.ru/en/