max_clients and keep alive

[Tristan Griffiths]

> -----Original Message-----
> From: owner-nginx at sysoev.ru [mailto:owner-nginx at sysoev.ru] On Behalf
Of
> Maxim Dounin
> Sent: Monday, 18 May 2009 9:07 PM
> To: nginx at sysoev.ru
> Subject: Re: max_clients and keep alive
> 
> Hello!
> 
> 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?
> 
> Yes.
> 
> 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).
> 
> Maxim Dounin

CentOS 5.3 kernel-PAE

[root at lb1 ~]# sysctl fs.file-max
fs.file-max = 400136

And that's the default setting!

Thank you for your help Maxim.