On Sat, Sep 22, 2012 at 07:37:03PM +0400, malc wrote:

On Sat, 22 Sep 2012, Gabriel Paubert wrote:

quoted

On Sat, Sep 22, 2012 at 02:12:42PM +0400, malc wrote:

quoted

On Sat, 22 Sep 2012, Segher Boessenkool wrote:

quoted

quoted

Is it possible to determine if _native_ isel is available from userspace
somehow?

Just try to execute one and catch the SIGILL?

Unfortunately my kernel emulates ISEL for me in this case, so i don't
get any SIGILLs.

Perform a few isels in a loop between a couple of mftb and measure the 
shortest time it takes. Any emulation will take tens of timebase ticks,
hardware implementation will return very small values, perhaps even
0 depending on the relationship between core and timebase frequencies.

I don't remember whether it's necessary inserting an isync between the
two mftb. I believe that even on the most OOO machines, two mftb in
a row will not be reordered to the point that the second executes before 
the first.

Thanks for suggestion, but i'd rather not play with heuristics.

It sounds like the sort of thing that ought to be in the ELF aux
vector, but I don't know if it actually is.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson