On 03/12/2015 06:16 PM, Florian Weimer wrote:

I looked at GCC, and -mtune=atom is actually -mtune=bonnell, and there
is now -mtune=silvermont.  Bay Trail and Avoton/Rangeley, the current
SoC families, belong to Silvermont, not Bonnell.
Well, to reach the largest possible user-groups, you need to compromise and balance the trade-offs.

So far. -mtune=atom seems to have worked well, with many users probably not even having noticed it.

That said, to me this would mean, you'd have to prove the other -mtune= options provide a measurable performance increase on those cpus/SoC without breaking backward compatibility on older HW.

As far as the switch to -mtune=atom is concerned, I don't know if was measureable, but it wasn't user-sensible on Atoms nor on i686s.

(And no, i686 binaries aren't just for enthusiasts.  I expect that users
who run 32-bit software with them on x86_64 installations are also
important.)
I do not agree. On the user-side, i686 binaries on x86_64 are a band-aid to help out on x86_64s in those rare occasions, when x86_64 binaries are not available (In most cases proprietary SW)

The major difference to users on real i686-cpus, is real i686-cpus typically are low-end CPUs, which - in comparison to x86_64-CPUs - suffer from lack of cpu-power. I.e. there a performance boost may play a different, more significant role than for i686-binaries on x86_64.

Ralf



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