openldap-software May 2010 archive
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openldap-software: RE: pls help: performance tuning

RE: pls help: performance tuning

From: ST Wong (ITSC) <ST_at_nospam>
Date: Wed May 12 2010 - 14:08:27 GMT
To: "Howard Chu" <>, "Aaron Richton" <>

Hi all,

Thanks for your help.

Regarding the "too many executing" source, it is an anti-spam/anti-virus
gateway blackbox that performs recipient checking using ldap query.
I'm afraid it's difficult to change her behaviour to split out hundreds
of operations over multiple connections. I'm check the product manual
of this blackbox, but probably won't be able to change it. Besides,
there are some other deferring operations logged from the same source:

11:May 10 03:09:38 fiesta slapd[31600]: connection_input: conn=633362
deferring operation: pending operations
11:May 10 03:04:56 fiesta slapd[31600]: connection_input: conn=712193
deferring operation: binding

The slapd doesn't respond or respond slowly when the problem occurs.
The servers each has 4 GB RAM.
Here comes some setting in slapd.conf and DB_CONFIG:

sizeLimit 50
timeLimit 600
cacheSize 1000000
checkPoint 1024 10
IDLcacheSize 3000
threads 32
sockbuf_max_incoming 4194303

set_cachesize 2 0 1
set_lg_bsize 20971520
set_lg_max 83886080
set_lg_regionmax 2621440
set_lk_max_locks 10000
set_lk_max_objects 5000

Would like to know if there is any problem with the setting.
Thanks again.
/ST Wong

-----Original Message-----
[] On
Behalf Of Howard Chu
Sent: Wednesday, May 12, 2010 2:25 AM
To: Aaron Richton
Cc: ST Wong (ITSC);
Subject: Re: pls help: performance tuning

Aaron Richton wrote:
> On Tue, 11 May 2010, ST Wong (ITSC) wrote:
>> I currently set thread in slapd.conf to 32 (default x 2). While I
>> think shouldn't modify SLAP_MAX_WORKER_THREADS, I tried to increase
>> no. of threads, at the cost of read performance. Besides, after
>> increasing thread to over 32, say 100, I got warning of "threads
>> larger than twice the default".
>> Would like to know the recommended way to tune the system in our
>> Would anyone pls help?
> "Recommended way to tune the system" is quite the slippery slope, but
> here goes nothing...

Note that the "too many executing" message refers to the number of
operations executing on a single connection. The first thing to do is
find out why this single connection is so busy. Well behaved clients
would not be spitting out hundreds of operations over a single
connection all at once.

> It sounds like you're focusing primarily on parallelism, which
> certainly has its merits. But I might sooner look at latency per
> operation. For example, with loglevel stats, you should have visiblity

> of client operations that are taking too long (i.e. delay until RESULT
> Perhaps an application started searching a field that isn't properly
> indexed, for example.
> Also, you don't mention results from looking for obvious bottlenecks
> (spindles, bus, cpu, etc.). For example, if you're waiting on hard
> drives, adding more threads is unlikely to help and in many cases
> would hurt. The likely solution there, short of a hardware upgrade, is

> adding more replicas (which also has benefits for redundancy/HA
> concerns, in addition to alleviating hardware limitations).
> Finally, you mention that you're using BerkeleyDB. You should post the

> size of your working set and your DB_CONFIG parameters. A 4-core
> system sounds fairly modern, it generally shouldn't be going to
> disk...if DB_CONFIG is not tuned accordingly, that would drastically
> affect performance. You can get some ideas for DB_CONFIG tuning in the

> FAQ-O-Matic and list archives.

-- -- Howard Chu CTO, Symas Corp. Director, Highland Sun Chief Architect, OpenLDAP