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Re: Searches with dereferncing causing high CPU load.

To: Mark Cairney <Mark.Cairney@ed.ac.uk>
Subject: Re: Searches with dereferncing causing high CPU load.
From: Andrew Findlay <andrew.findlay@skills-1st.co.uk>
Date: Mon, 16 Nov 2015 18:10:32 +0000
Cc: openldap-technical@openldap.org
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In-reply-to: <5649F287.3010500@ed.ac.uk>
References: <5649F287.3010500@ed.ac.uk>
User-agent: Mutt/1.5.21 (2010-09-15)

On Mon, Nov 16, 2015 at 03:13:11PM +0000, Mark Cairney wrote:

> We're having severe performance issues for any query with alias
> dereferencing set to "always".
> 
> Any query with this causes the CPU to spin up to 100% and if we have a
> number of these concurrently the machine will become unresponsive.

I hit something similar a while ago using mdb:

http://www.openldap.org/its/index.cgi/Software%20Bugs?id=8146

> We're using OpenLDAP 2.4.42 with the old hdb backend.
> 
> We do have a large number of aliases (~63,000). Could this be the cause?

It would be worth checking that you have indexed the objectclass attribute.

I prefer to avoid aliases...

Andrew
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References:
- Searches with dereferncing causing high CPU load.
  - From: Mark Cairney <Mark.Cairney@ed.ac.uk>

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