[RFC 0/3] powerpc: memory copy routines tweaked for Cell

[Mark Nelson]

On Fri, 20 Jun 2008 09:49:29 am Mark Nelson wrote:
> On Thu, 19 Jun 2008 09:53:16 pm Arnd Bergmann wrote:
> > On Thursday 19 June 2008, Mark Nelson wrote:
> > > The plan is to use Michael Ellerman's code patching work so that at runtime
> > > if we're running on a Cell machine the new routines are called but otherwise
> > > the existing memory copy routines are used.
> > 
> > Have you tried running this code on other platforms to see if it
> > actually performs worse on any of them? I would guess that the
> > older code also doesn't work too well on Power 5 and Power 6, so the
> > cell optimized version could give us a significant advantage as well,
> > albeit less than another CPU specific version.
> > 
> > 	Arnd <><
> > 
> 
> I did run the tests on Power 5 and Power 6, and on Power 5 with the
> new routines, the iperf bandwidth increased to 7.9 GBits/sec up from
> 7.5 GBits/sec; but on Power 6 the bandwidth with the old routines
> was 13.6 GBits/sec compared to 12.8 GBits/sec...

After running the tests again I get a similar result, where on Power 6
the new routine is slower than the old one.

I'll spend some time doing tests to see if we can come up with a
routine that works well on Power 6 too.

Mark