RE: /CLR floating point performance, inter-assembly function call performance

From: Yan-Hong Huang[MSFT] (yhhuang_at_online.microsoft.com)
Date: 05/06/04 

Date: Thu, 06 May 2004 06:09:57 GMT

Hello Bern,

Generally speaking, the v1 JIT does not currently perform all the
FP-specific optimizations that the VC++ backend does, making floating point
operations more expensive for now. That may be why managed->managed is more
expensive than managed->unmanaged in your test.

So for areas which make heavy use of floating point arithmetic, please use
profilers to pick the fragments where the overhead is costing you most, and
Keep the whole fragment in unmanaged space.

Also, work to minimize the number of transitions you make. If you have some
unmanaged code or an interop call sitting in a loop, make the entire loop
unmanaged. That way you'll only pay the transition cost twice, rather than
for each iteration of the loop.

By looking into ILCode, we can see that when InterOping, there are some
extra IL instructions. So minimizing the number of transitions can save
many IL instructions and improve performance.

For some more information, you can refer to this chapter online:
"Chapter 7 ¡ª Improving Interop Performance"
http://msdn.microsoft.com/library/en-us/dnpag/html/scalenetchapt07.asp?frame
=true#scalenetchapt07 _topic12

Hope that helps.

Best regards,
Yanhong Huang
Microsoft Community Support

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