Re: Maximum size of the primary thread pool

[Howard Chu <hyc@symas.com>]

Rajarshi Chaudhuri wrote:
> Hi,
>
>  
>
> Maximum size of the primary thread pool - the default is 16. Is it 
> recommended to increase this value to higher ones like 32/64 etc.

We would never recommend any particular value for any particular purpose. 
Without knowing the specifics of a system environment and usage patterns, 
such recommendations would be meaningless.

> Is 
> there any loose relation between the RAM and OS and the thread pool size 
> that I need to consider.

Yes, each thread uses 4 or 8MB of memory for its runtime stack. (8MB on 64 
bit machines). Plus there are a variety of other modules that allocate things 
on a per-thread basis.

> Simply, is there any guideline on this thread pool size and it’s 
> implications?

The guideline is "test your server at varying configurations and choose what 
works best for you." The effectiveness of threading varies with machine 
architecture, OS revision, and C library revision. Increasing the thread 
count eventually reaches a point of zero-gain as the thread scheduling 
overhead starts to overshadow the time spent actually executing user code. 
This is a fundamental feature of threading, on any system with any software.

> Rajarshi Chaudhuri
> Genesys Telecommunications Lab, Inc
> rajarshi@genesyslab.com <mailto:rajarshi@genesyslab.com>

--
  -- Howard Chu
  Chief Architect, Symas Corp.  http://www.symas.com
  Director, Highland Sun        http://highlandsun.com/hyc
  Chief Architect, OpenLDAP     http://www.openldap.org/project/