Re: i686 quirk for AMD Geode

Matteo Croce
2009-11-08T18:43:07Z

On Fri, Nov 6, 2009 at 5:44 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 11/06/2009 06:59 AM, Matteo Croce wrote:
>> indeed it has MMX, MMXEXT and CMOV, just lacks the long NOP instruction (NOPL).
>
> MMX and MMXEXT are hardly hallmarks of i686, which leaves only cmov.
> I'm somewhat wondering about the general value of this patch; is i686
> code really that much faster on Geode that it's worth it?
>
>        -hpa
>
> --
> H. Peter Anvin, Intel Open Source Technology Center
> I work for Intel.  I don't speak on their behalf.
>
>

There is a small advantage, but considering that GCC isn't much geode aware yet
there is stil room for improvement IMHO:

root@alix:/usr/src/dist# ll
totale 257M
-rwxr-xr-x 1 1000 src 93K 8 nov 2009 bzip2-i586
-rwxr-xr-x 1 1000 src 93K 8 nov 2009 bzip2-i686
-rwxr-xr-x 1 1000 src 60K 8 nov 2009 gzip-i586
-rwxr-xr-x 1 1000 src 60K 8 nov 2009 gzip-i686
-rw-r--r-- 1 1000 src 256M 8 nov 2009 linux-2.6.31.5.tar
-rwxr-xr-x 1 1000 src 90K 8 nov 2009 lzma-i586
-rwxr-xr-x 1 1000 src 94K 8 nov 2009 lzma-i686
root@alix:/usr/src/dist# time cat linux-2.6.31.5.tar >/dev/null

real 0m10.168s
user 0m0.030s
sys 0m1.390s
root@alix:/usr/src/dist# time ./gzip-i586 -9 < linux-2.6.31.5.tar >/dev/null

real 5m22.331s
user 5m10.820s
sys 0m11.170s
root@alix:/usr/src/dist# time ./gzip-i686 -9 < linux-2.6.31.5.tar >/dev/null

real 5m3.737s
user 4m51.880s
sys 0m11.510s
root@alix:/usr/src/dist# time ./bzip2-i586 -9 < linux-2.6.31.5.tar >/dev/null

real 9m16.539s
user 9m4.410s
sys 0m11.760s
root@alix:/usr/src/dist# time ./bzip2-i686 -9 < linux-2.6.31.5.tar >/dev/null

real 8m48.682s
user 8m34.950s
sys 0m13.260s