[fedora-arm] Fedora 20 for Raspberry Pi????

[Richard W.M. Jones]

On Wed, Jan 01, 2014 at 12:21:30PM -0800, Sean Omalley wrote:
> They are a problem. It is a performance issue at the very least on
> =ALL= platforms. There is a cost even on Intel's platform for
> alignment errors, they just fix them up in hardware so it isn't as
> big of a performance hit. It might be 5 cycles instead of 20.

On Intel Sandybridge and up there is no penalty:

http://www.agner.org/optimize/blog/read.php?i=142&v=t

On earlier Intel processors it's not significant:

http://lemire.me/blog/archives/2012/05/31/data-alignment-for-speed-myth-or-reality/

Anyway, you are optimizing far too early.  If there's a performance
problem, run 'perf', find out that it's caused by X where X might be
the big misalignment penalty on ARM or many other things, then fix
that.

There's no need to go on a huge crusade to fix every last mis-
alignment, because that will involve vast hours of programmer effort
for no measurable gain.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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