i386-class support changed in F-13?

[David Michael]

Hi,

On Wed, Jun 2, 2010 at 11:42 AM, Richard W.M. Jones <rjones at redhat.com> wrote:
> I wonder what the performance impact is.  NOPL appears to be a
> variable length NOP (no-op).  Obviously a very useful instruction for
> things like alignment, and gcc seems to stuff lots of them into the
> code:
>
>  $ objdump -d /bin/ls | wc -l
>  16867
>  $ objdump -d /bin/ls | grep nopl | wc -l
>  369
>
>  369/16867 ~ 2%
>
> This is not a very fair comparison because we'd want to know how
> frequently NOPL is executed, but I hope it shows that these
> instructions are not infrequent.

  I recall checking this when F12 was declared to go i686 but retain
support for Geode LX CPUs.  NOPLs were common in x86_64, but seemed to
be very infrequent in 32-bit land (which is what would run on a Geode
anyway).

  To see if this is still the case, I downloaded and extracted F13's
32-bit coreutils, and no binary appears to contain a single NOPL.
(Though I get a similar result as your test with x86_64.)

objdump -d {,usr/}{,s}bin/* | grep -Fc nopl
0

> Having said that, AMD Geodes are slowwwwww anyway ...

  I wouldn't exactly use it as a gaming rig, but a silent wireless
computer on <5W power can always be used for something.