How to make maximum benefit from Hyper-Threading in .Net

Question

Not sure if that is even possible in a managed language, but is it possible to actually make an application perform better in the presence of hyper threading ?

Is there something specific that can be done in the code ? , maybe some functions run better than other in HT environments ?

I know that to benefit from multi-threading, all that is needed is to spawn new threads to perform heavy cpu tasks, but I am not sure what is required for HT ?

Answer 1

Depends a lot on the actual hardware you have. Read Be aware: To Hyper or not to Hyper for a more in dept analysis. Slava's point in the link is that in HT the virtual cores share the cache and a the virtual core workload can trash the cache of the 'main' core and, even though it can do at best some 20% of workload compared with the main core, becuase it evicts the hot cache of the main core, it cause the main core to stall and overall results in worse performance than w/o HT.

But a lot of things have changed since the article was posted, HT post Nehalemis significantly better.

I know that to benefit from multi-threading, all that is needed is to spawn new threads to perform heavy cpu tasks

That is quite a naive view. You must read Rick Vicik articles on high performance windows programs (they apply to managed apps too) and you must absolutely understand CPU Caches and Why You Care.