Red Hat Directory Server 7.1 Performance Tuning and Sizing Guidelines
•Import cache: specified as nsslapd-import-cachesize. If you do not do online import, then memory allocated for the dbcache can be used for import cache. There is no need to allocate memory for the import cache in addition to the dbcache.
Tuning Recommendations
This section discusses how to tune some of the very important RHDS attributes.
nsslapd-threadnumber
Here is some information about nsslapd-threadnumberfrom document: Red Hat Directory Server 7.1 Configuration, Command, and File Reference †
•nsslapd-threadnumber
Defines the number of operation threads that the Directory Server will create during startup. The nsslapd-threadnumber value should be increased if you have many directory clients performing time-consuming operations such as add or modify, as this ensures that there are other threads available for servicing short-lived operations such as simple searches. This attribute is not available from the server console.
Entry DN: cn=config
Valid Range: 1 to the number of threads supported by your system
Default Value: | 30 |
Syntax: | Integer |
Example: | nsslapd-threadnumber: 60 |
One common misconception is that more threads are better. When there are too many threads configured, thread contention may affect the performance. As you can see from the graph below, after certain point, as the number of threads increases, the search throughput decreases in this particular controlled test. In this case, the best performance occurs when nsslapd-threadnumberis set to 6 or 8 (on a Montecito-based test bed with 8 CPUs). Based on the performance test experiment, the best exact search performance occurs only when nsslapd- threadnumber is tuned close to the number of CPUs. This performance characteristic is verified with up to 8 CPUs on an Montecito-based test bed.
When tuning this parameter, consider this:
•if the directory only serves non-SSL based search requests, tune nsslapd-threadnmberstarting from where it equals number of CPUs.
•if the directory needs to handle time-consuming operations which require threads to be blocked for a long time, such as SSL based searches, tune up nsslapd-threadnumber.
•if there are large numbers of clients concurrently requesting connections, tune up nsslapd- threadnumber.
•if you experience low CPU utilization under a heavy load, or slow response time, try to tune up nsslapd- threadnumber and see if performance improves.
†Hewlett-Packard Company, “Red Hat Directory Server 7.1 Configuration, Command, and File Reference”. http://docs.hp.com/en/7119/ds71cli.pdf
