FCStacks influence on number of wavefronts in-flight

Discussion created by Raistmer on Sep 18, 2010
Latest reply on Sep 22, 2010 by himanshu.gautam
what values is too high?

FCStacks - The number of flow control stack size used by the kernel (only for GPU device). This number may affect the number of wavefronts in-flight. To reduce the stack size, reduce the amount of flow control nesting in the kernel.
Could someone give some numbers, please. How this number will affect the number of simultaneously executed wavefronts on SIMD ?
For example one of my kernels has FCStacks ==2, another one FCStacks ==6.
In what case this number will be limiting factor?

EDIT: the kernel with FCStacks ==6 has pretty high GPR usage too, 55 GPRs used.
What will limit number of wavefronts in this case? GPR usage or FCStacks value?
And how many wavefronts per SIMD I could expect ?