VM config managment problems...
Ian Piumarta
ian.piumarta at inria.fr
Wed Sep 10 15:04:43 UTC 2003
On Wed, 10 Sep 2003, John M McIntosh wrote:
> > Hands up anyone running Unix on a 68k machine...?
> Wait wait there is hand here in the corner. I've got TWO OpenBsd 68K
> boxes running. And I know Bruce ONeel was running a 68K NetBSD box
Ah, okay. I think 3 counts as a quorum. ;)
So what are the benchmark results with/out the jump table pointer
modification on all of the above machines?
> > Even better, check benchmark times. Removing instructions has been
> > known to make things slower. (Too many hazards in the pipeline
> > end at the same time.)
> Mm that is interesting, have you observed that on the powerpc?
Yes, but only on older (600 series) cpus -- if I remember correctly.
(There's something about this in the architecture manual too; if you
_really_ want I can try to dig up the ref.) On the 700s my experience is
that you reach a critical density above which removing instructions makes
no measurable difference in speed (which I think is what we saw when we
tried the code on my G3). I don't know how the 7000s are supposed to
behave, but I'm sure it's no worse than the 700s. (Is Tim O reading
this?? ;)
Cheers,
Ian
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