linux-kernel - Re: i686 quirk for AMD Geode

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Date:	Sun, 8 Nov 2009 19:42:48 +0100
From:	Matteo Croce <technoboy85@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: i686 quirk for AMD Geode

On Fri, Nov 6, 2009 at 5:44 PM, H. Peter Anvin <hpa@...or.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@...x:/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@...x:/usr/src/dist# time cat linux-2.6.31.5.tar >/dev/null

real    0m10.168s
user    0m0.030s
sys     0m1.390s
root@...x:/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@...x:/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@...x:/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@...x:/usr/src/dist# time ./bzip2-i686 -9 < linux-2.6.31.5.tar >/dev/null

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