Monitoring and Tuning Your Server

Optimizing Thread Values

By default, the IIS 5.0 process creates up to four threads per processor. IIS 5.0 continually adjusts the number of threads in its process in response to server activity. For most systems, this tuning is sufficient to maintain the optimum number of threads, but you can change the maximum number of threads per processor, if your system requires it. If the threads in the IIS 5.0 process appear to be overworked or underutilized, consider these tuning strategies:

If nearly all of the threads of the IIS 5.0 process are busy nearly all of the time, and the processors are at or near their maximum capacity, consider distributing the workload among more servers. You can also add processors, but do so cautiously. Unnecessary or underused processors will degrade performance, not improve it.
If nearly all threads appear busy, but the processors are not always active, consider increasing the maximum number of threads per processor. Do not increase the maximum number of threads unless you have processors with excess capacity. More threads on the same number of processors cause more interrupts and context switches, and result in less processor time per thread.

To adjust the maximum number of threads in the IIS 5.0 service process, use a registry editor to add the MaxPoolThreads entry to the registry. MaxPoolThreads does not appear in the registry unless it is added to the following:

HKEY_LOCAL_MACHINE
\System
\CurrentControlSet
\Services
\Inetinfo
\Parameters

Caution Do not use a registry editor to edit the registry directly unless you have no alternative. The registry editors bypass the standard safeguards provided by administrative tools. These safeguards prevent you from entering conflicting settings or settings that are likely to degrade performance or damage your system. Editing the registry directly can have serious, unexpected consequences that can prevent the system from starting and require that you reinstall Windows 2000. To configure or customize Windows 2000, use the programs in Control Panel or Microsoft Management Console (MMC) whenever possible.

MaxPoolThreads is calculated in units of threads-per-processor. Do not set this value below 2 or above 20. Continue monitoring the system carefully to make sure that changing the number of threads achieves the desired effect.