[linux-fbdev] Re: readl() and friends and eieio on PPC

Paul Mackerras paulus at cs.anu.edu.au
Thu Aug 12 15:00:46 EST 1999

Richard Henderson <rth at cygnus.com> wrote:

> But it isn't zero cost.  It's not high cost, but that's not the same
> thing.

Show us the numbers?

I'm starting to sound like Larry McVoy, I know. :-)

The measurements I did showed no measurable difference in performance
for copying stuff around a framebuffer on PPC (Richard, I guess you
may not have seen that post).  As far as PPC is concerned, I am
unwilling to break drivers for the sake of an infinitesimal
performance gain.  I don't believe the frame-buffer guys will actually
see any measurable improvement in performance from taking out the
eieio from readl/writel on PPC.

Of course, it may be different on alpha, and I would be very
interested to know how big the effect is there.


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