PowerPC FP handling weakness.

[Eric Valette]

Joel Sherrill wrote:

> > I'm affraid deffered FPU context switching has never been tested on
> > 60x/7xx. Maybe I can be wrong...
> 
> I think that in a system where all tasks are FP deferred switching is
> equivalent to on every switch.  Think about it.  All deferred switching
> says is that we won't save the context until another FP task is switched
> in.  This is every time.  Not as clear as it should be but technically
> OK.

No I disagree. FP context switching is performed when the newly tasks
really use the FPU. Saying a thread is a FP task does not mean it will
use the FP each time it is scheduled...

All I wanted to say is that deferred FP context saving remove the need
of hardcoding whether a thread is FP or not and perform a better job by
saving FP context only when needed.

Did I miss something?

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