Tuesday, January 21, 2003

SingleThreadedModel may be usefull

While doing the per/thread hacks on the JSP tag pool - and same for collecting statistics on per thread basis, to avoid sync - I just realized - the so bashed STM servlet may be actually one of the best things...

Of course, STM doesn't avoid the complexity of programing in a multithreaded environment - and it is probably even more vulnerable to errors. It is also much more complex to implement and harder to use. If you use STM, you must find ways to agregate the data from the multiple instances, and it may use more memory.

The big benefit is that with STM you basically get a per/thread worker - and do a lot of stuff with no sync calls. A good implementation would do a sync to get the STM - but that can be improved by using ThreadLocal or the new ThreadWithAttributes.

Not doing sync calls at runtime - or at least during the critical path - will have a visible impact on loaded sites ( if done right ). You have to pay for that in terms of complexity when you want to take the fields from all those servlet instances and

use them - that's where you may need sync and a lot of complex code.

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