Andrew Morton <[email protected]> writes:
>
> We do have the `used_math' optimisation in there which attempts to avoid
> doing the FP save/restore if the app isn't actually using math. But
> <ancient recollections> there's code in glibc startup which always does a
> bit of float, so that optimisation is always defeated. There was some
> discussion about periodically setting tasks back into !used_math state to
> try to restore the optimisation for tasks which only do a little bit of FP,
> but nothing actually got done.
Actually we reset the flag on every context switch, so that works just fine.
But I was considering to do it less often so that we switch the FP
state non lazily for FP intensive processes and avoid the overhead
of all these exceptions.
-Andi
P.S.: Original profile data looks a bit fishy. Normally avoiding a single
function call should not make tht much difference unless you call
it in a inner loop, but that is not the case here.
-
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