max_clients and keep alive

Arvind Jayaprakash work at
Wed Jun 10 21:31:30 MSD 2009

On May 18, Maxim Dounin wrote:
>On Mon, May 18, 2009 at 09:54:34AM +1000, Tristan Griffiths wrote:
>> Hello,
>> Trying to better understand the worker_processes and worker_connections
>> settings.
>> We have always run Nginx with worker_processes 4 and worker_connections
>> 1024 on a dual Xeon 2.4GHz with Hyper Threading. In the documentation,
>> it suggests it is better to run worker_processes 2 and
>> worker_cpu_affinity 0101 1010 for a dual HTT machine but according to
>> the formula (max_clients = worker_processes * worker_connections) that
>> would effectively halve the connections we can support to clients and
>> backend servers.
>> We regularly see more than 2000 keep alive connections at any point in
>> time, so do keep alive connections count towards the maximum client
>> connections?
>Feel free to increase worker_connections.  Note also that worker 
>connections are cheap - they consume only about 200 bytes of 
>memory per connection, so setting something like 16384 isn't a 
>big deal.
>The only thing to keep in mind is that your OS settings should be 
>tuned as well or this may lead to bad results.  E.g. make sure 
>that worker_connections are less than available to nginx process 
>number of file descriptors (kern.maxfilesperproc under FreeBSD).

If the master process starts as root and worker_rlimit_nofile is set,
then does any of system limit wrt fd matter?

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