Re: "threads" directive OpenLDAP 2.0.* & 2.1.*

[Quanah Gibson-Mount <quanah@symas.com>]

--On Monday, November 07, 2005 9:26 AM -0500 Robert Petkus 
<rpetkus@bnl.gov> wrote:

> Quanah Gibson-Mount wrote:
>
> > low.  The default in OpenLDAP 2.2 and 2.3 is 16, I don't recall
> > offhand the
> > default in 2.1.  I generally don't advise going above 16 threads, and
> > recent testing in the Symas benchmarking labs seems to indicate that a
> > lower setting is actually better, as it reduces contention in the backend
> > database.
> Really?  I've found that the default of 16 threads is inadequate in a
> large environment -- at least when using a ldap proxy in front, the load
> is inversely proportional.  Are the benchmarking results public?

As with anything, it entirely depends on your specific configuration.  What 
I was looking at in this benchmark is an OpenLDAP server doing only one 
thing -- Having a bdb database that returns data, no proxying involved.

The results from the same database/server at the following thread levels 
were:

8 threads (20 querying clients): 8,726 reads/second
12 threads (20 querying clients): 6,583 reads/second
20 theads (20 querying clients): 5,904 reads/second


Results from oprofile indicated that with both 12 and 20 threads, the 
majority of time was spent in BDB database locks.  With 8 threads, the 
highest percentage  time was spent in the slapd libraries.


--Quanah

--
Quanah Gibson-Mount
Product Engineer
Symas Corporation
Packaged, certified, and supported LDAP solutions powered by OpenLDAP:
<http://www.symas.com>