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)?
>
> 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).
>   
The DB_CONFIG is the same for all databases. The first database has 
about 70K entries and the others only have a couple of entries. What is 
interesting is that queries to the all databases are really slow even 
though there is almost no data in two of them.  I am have tried the 
2.4.18 packages from Buchan Milne on RHEL5 and they seem to work fine.

The performance seems to be a great deal worse for none index searches. 
Searching for entries using the object class takes about 1s, however, 
using an attribute and a wild card takes 26s.  The performance of both 
become worse with each successive query and this affects all databases 
no matter which one queried.

Thanks for your help

Laurence