Re: Query performance degrades over time.

[Laurence Field <Laurence.Field@cern.ch>]

masarati@aero.polimi.it wrote:
> > We are experiencing a decay in query performance over time using
> > OpenLDAP 2.3.43 on CentOS 5.
> >
> > After populating the database with about 70 000 entries, the query
> > response time for one entry is about 0.4s. After about two hours the
> > same query takes over 1s.  The slapd.conf file and DB_CONFIG files that
> > we use can be found at the following URLs.
> >
> > http://svnweb.cern.ch/trac/gridinfo/browser/bdii/trunk/etc/bdii-slapd.conf
> > http://svnweb.cern.ch/trac/gridinfo/browser/bdii/trunk/etc/DB_CONFIG
> >
> > Does anyone have an idea about what is happening.
> >     
>
> Not sure whether it matters or not, but your DB_CONFIG's set_cachesize
> looks very small, about 50MB.  Are the same DB_CONFIG settings used for
> all databases?  What database, of the 3 defined in your slapd.conf, is
> suffering from this problem?  Are critical searches related to indexed
> attrs?  Can you reproduce the problem with recent releases (e.g. 2.4.19)?
>   
So here are the results of the performance test.  The the machines used 
were Xeon 2.33GHz 2 quad core CPUs with 16 GB RAM. The database was 
populated with 80K entries, approximately 70MB. A query for all entries 
was run using a single loop with a 5s sleep. The resulting graphs of the 
network utilization for the different LDAP versions can be found at the 
URLs below.

http://lfield.web.cern.ch/lfield/2.3.43.png
http://lfield.web.cern.ch/lfield/2.4.18.png

The decrease in throughput corresponds to an increase in the response 
time. Why is the performance of version 2.3.43 decreasing over time?

Thanks


Laurence

> Also, I note that only in the first database you define an equality index
> on objectClass.  This is instrumental for decent performances of slapd, as
> documented in slapd-bdb(5) (the presence index on objectClass is
> pointless).
>
> p.
>
>