Re: strange performance problem

[Peter Marschall <peter@adpm.de>]

Hi,

have you only tred it with back-dbd od with back-ldbm too ?
Just to get an idea if it is more related to the core of slapd or to a
specific backend.

Peter



On Sunday 23 March 2003 14:47, Cuong bui wrote:
> Hello all,
>
> I'm doing some research on openldap to see if it's suitable for a certain
> kind of application. This application requires more write operations from
> the ldap server then an 'average' usage of ldap.
>
> For this purpose i've written an multithreaded application to simulate
> simultaneous access to the ldap server. This application creates an
> variable number of threads that simulate an client. There's a central queue
> of task that have to be performed. The queue has 3 kind of task (for now).
>
> 1. filter task. Simple search on a certain key
> 2. modify task. modification of a 'record'.
> 3. authentication task. (simple bind and unbind, simple authentication for
> now)
>
> The task queue is built in such a way that the type of tasks are mixed with
> eachother.
>
> i've generated a test dataset of 50.000 records and the .bdb files have
> been copied to an other location (ofcourse  when the server is offline) in
> order to restore data (instead of regenerating the test dataset, it can now
> be copied back).
>
> The testruns were very promising. for instance with 1000 tasks (300 filter,
> 600 modification, 100 authentication) and 32 threads only took 9 seconds to
> complete. However performing this same test a few times gives me a rather
> surprise effect. the first 4 runs all took about 9-13 seconds to complete.
> The 5th run and up takes up to 5 mins (!) or more.  Simple searches with
> ldapsearch takes up a few mins (after 4 testruns). (before that they only
> took a fraction of a second).
>
> during the first 4 testruns the openldapserver used 98% cpu processing
> time. (seen in top) After the initial 4 runs, slapd only consumes 40%-75%
> cpu processing time. somethimes it's even dropping to a few %.
>
> The only way to get slapd working 'normal' again, is to shutdown the server
> and restore the dataset. I have defined an index on  the field that i'm
> filtering on. (without it searches will take a very long time to complete).
>
> The test server consist of a pentium 4 2,53 ghz running gentoo linux with
> kernel 2.4.20 and ultra dma (enabled) hdd   with 512 MB ram. Openldap
> 2.1.16 was running on this machine. (but also tested with 2.1.12 and 2.1.15
> they all gave this result) BDB was chosen as backend for this test.)
>
> The testclient consist of an pentium 4 1,8ghz with gentoo linux running
> kernel 2.4.19. The 2 systems were connected on a 100 mbit (switched)
> network. All the software were compiled with g++ 3.2.1
>
> Has anyone an explanation for this behaviour ? Is this a known problem ?
> All hints are welcome.
>
>
> Thank in advance (and for your time)
> Cuong
>
> btw: are there any documentation on implementations details of openldap ?
> if yes, where can i find them :) Other documentation that might explain
> what i'm seeing is also (very) welcome.

-- 
Peter Marschall
eMail: peter@adpm.de