Hi Andy,
For the Athlon64 system, I get the following:
$ gcc -o cpuid cpuid.c
$ ./cpuid
00000001:68747541:444d4163:69746e65
00020f32:01020800:00000001:178bfbff
I also see similar behaviour on an Intel Xeon system also using the
linux-x86_64 target. Using the 8192 byte column from the speed output for
aes-128-cbc, I get the following:
0.9.8k: 209117.18k
1.0.0 beta2: 98832.30k
1.0.0 beta2 (no-asm): 185606.83k
For that system, the cpuid output is:
$ ~/cpuid
0000000a:756e6547:6c65746e:49656e69
00010676:03040800:000ce3bd:bfebfbff
0c000121:01c0003f:0000003f:00000001
On Wed, May 06, 2009 at 15:13:32 -0500, Andy Polyakov wrote:
> > I'm not sure if this topic has been brought up previously, but I've
> > noticed that the AES performance with the linux-x86_64 target seems to
> > have dropped relative to 0.9.8k. This is on an AMD Athlon64 X2 with GCC
> > 4.1.2.
>
> Could you compile attached problem and submit its output? This is for
> reference and to double-check that everything is detected correctly.
>
> > I'm curious as to the cause of this and whether it is intentional (to
> > mitigate a timing attack, perhaps)
>
> Bullseye. For further information see crypto/aes/asm/aes-596.pl, second
> half of commentary section.
>
> > or whether it is an accidental side-effect.
>
> No.
>
> > Strangely, the AES performance is actaully _better_ with the no-asm flag,
> > although not as good as 0.9.8k.
>
> But it would still be faster is C would implement equivalent code. A.
>
>
Content-Description: cpuid.c
> #include <stdio.h>
>
> main()
> { unsigned int eax,ebx,ecx,edx,max;
> max=0;
> __asm volatile ("cpuid" :
> "=a"(max),"=b"(ebx),"=c"(ecx),"=d"(edx):"0"(max));
> printf("%08x:%08x:%08x:%08x\n",max,ebx,ecx,edx);
> eax=1;
> __asm volatile ("cpuid" :
> "=a"(eax),"=b"(ebx),"=c"(ecx),"=d"(edx):"0"(eax));
> printf("%08x:%08x:%08x:%08x\n",eax,ebx,ecx,edx);
> if (max<4) return 0;
> eax=4; ecx=0;
> __asm volatile ("cpuid" :
> "=a"(eax),"=b"(ebx),"=c"(ecx),"=d"(edx):"0"(eax),"2"(ecx));
> printf("%08x:%08x:%08x:%08x\n",eax,ebx,ecx,edx);
> }
--
Iain Morgan
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