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

Mark Nelson markn at au1.ibm.com
Fri Jun 20 09:49:29 EST 2008

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...

I also couldn't get the updated routines to boot on 970MP without
removing the dcbz instructions.

I'll investigate more and also rerun the tests again



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