[RFC] Moving toward smarter disabling of FPRs, VRs, and VSRs in the MSR

[Josh Boyer]

On Sat, Mar 14, 2009 at 09:45:51AM +1100, Benjamin Herrenschmidt wrote:
>
>> If these applications are aware they are heavy users (of FP, VMX, VSX)  
>> can we not use a sysctl()?  Doing so wouldn't be that difficult.
>> 
>> I think trying to do something based on a runtime heuristic sounds a  
>> bit iffy.
>
>Another option might be simply to say that if an app has used FP, VMX or
>VSX -once-, then it's likely to do it again and just keep re-enabling
>it :-)
>
>I'm serious here, do we know that many cases where these things are used
>seldomly once in a while ?

This seems reasonable to me.

>An if we do, maybe then a simple counter in the task struct... if the
>app re-enables it more than a few consecutive switches, then make it
>stick. I have the feeling that would work out reasonably well.

Gee.  That sounds like a runtime heuristic :)

josh