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From: David Jander <david.jander@protonic.nl>
To: linuxppc-dev@ozlabs.org
Subject: Efficient memcpy()/memmove() for G2/G3 cores...
Date: Mon, 25 Aug 2008 11:31:01 +0200
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Hello,

I was wondering if there is a good replacement for GLibc memcpy() functions, 
that doesn't have horrendous performance on embedded PowerPC processors (such 
as Glibc has).

I did some simple benchmarks with this implementation on our custom MPC5121 
based board (Freescale e300 core, something like a PPC603e, G2, without VMX):

...
unsigned long int a,b,c,d;
unsigned long int a1,b1,c1,d1;
...
while (len >= 32)
{
    a =  plSrc[0];
    b =  plSrc[1];
    c =  plSrc[2];
    d =  plSrc[3];
    a1 = plSrc[4];
    b1 = plSrc[5];
    c1 = plSrc[6];
    d1 = plSrc[7];
    plSrc += 8;
    plDst[0] = a;
    plDst[1] = b;
    plDst[2] = c;
    plDst[3] = d;
    plDst[4] = a1;
    plDst[5] = b1;
    plDst[6] = c1;
    plDst[7] = d1;
    plDst += 8;
    len -= 32;
}
...

And the results are more than telling.... by linking this with LD_PRELOAD, 
some programs get an enourmous performance boost.
For example a small test program that copies frames into video memory (just 
RAM) improved throughput from 13.2 MiB/s to 69.5 MiB/s.
I have googled for this issue, but most optimized versions of memcpy() and 
friends seem to focus on AltiVec/VMX, which this processor does not have.
Now I am certain that most of the G2/G3 users on this list _must_ have a 
better solution for this. Any suggestions?

Btw, the tests are done on Ubuntu/PowerPC 7.10, don't know if that matters 
though...

Best regards,

-- 
David Jander