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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 case.
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 lines).
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.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/