IIS 6 Peformance Paper
IIS 6 Peformance Paper - Worth the read
By Brett ‘brett’ Hill on IISFAQ Front Page
Papers from Microsoft are often hit and miss. Some are stellar and some are overbroad overviews filled with marketing jargon. This one, however, is well worth the read. He’s an excerpt from Web and Application Server Infrastructure - Performance and Scalability
COM General
With the new IIS 6.0 architecture, it is important to question some of the existing guidelines where COM is concerned. A major consideration is that, before Windows Server 2003, COM application components were configured (by default) to run out-of-processes from the caller. The default for COM applications is for them to run as Server Applications, executing in a DLLHost.exe process called into from the object instantiate, or over DCOM.
The performance downside of doing this for every method call, is that there are extra threads running on the system, and every call to a method must be marshaled across process boundaries. This is not noticeable on a small implementation with low request/transaction rates, but on a high volume, large multiprocessor, this kind of overhead can greatly decrease the overall scalability of the system.
Therefore, on Windows Server 2003, it is best to change the default configuration for a COM Server Application to Library Application to aid scalability of the calling per use of that application