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RE: Maximum size of the primary thread pool

Thanks Howard - I'll vary the pool size and watch the impact under load.


One more question regarding threads - is there a relation between the
concurrency directive and the threads directive in slapd.conf?

Rajarshi Chaudhuri
Genesys Telecommunications Lab, Inc
rajarshi@genesyslab.com
650.466.4860
 

-----Original Message-----
From: Howard Chu [mailto:hyc@symas.com] 
Sent: Thursday, February 08, 2007 3:45 PM
To: Rajarshi Chaudhuri
Cc: openldap-software@openldap.org
Subject: Re: Maximum size of the primary thread pool

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/