Re: -mtune option for Intel Nehalem

Re: -mtune option for Intel Nehalem

[Rayne]

I mostly just want to know if an option is avaliable for the Nehalem processors. If it happens that the newest version of GCC has such an option, then I can always upgrade to that version. I believe that Barcelona is an AMD processor, so I'm confused as to how that would work for an Intel Nehalem processor. As for -mtune=nocona, I've tried and there was no performance gain.

Thank you.

Regards,
Rayne


> Do you mean you want to use an old version of gcc, issued prior to the 
> advent of -mtune=barcelona? That would reduce your performance potential 
> for vectorized code. It should be obvious, as Nehalem came later than 
> Barcelona, that there would be no optimization for Nehalem in older 
> versions.
> You would have to experiment yourself to see whether -mtune=nocona helps 
> performance in your case. It's certainly not feasible to give you 
> recommendations covering all old gcc versions, even if we could guess the 
> other factors of your case.
>
>
>--
>Tim Prince


      

Re: -mtune option for Intel Nehalem

[Tim Prince]

On 4/12/2010 6:47 PM, Rayne wrote:
> I mostly just want to know if an option is avaliable for the Nehalem processors. If it happens that the newest version of GCC has such an option, then I can always upgrade to that version. I believe that Barcelona is an AMD processor, so I'm confused as to how that would work for an Intel Nehalem processor. As for -mtune=nocona, I've tried and there was no performance gain.
>    
Barcelona was the first of the recent CPUs which benefited consistently 
from 128-bit moves, aligned or unaligned, and Nehalem continued the 
trend. Hence the recommendation of the same option, if you are using 
auto-vectorization.  With current gcc, you could add -msse4.2 if you are 
hoping occasionally to generate code specific to Nehalem.

Re: -mtune option for Intel Nehalem

[Tim Prince]

On 4/11/2010 11:02 PM, Rayne wrote:
> Hi all,
>
> I can't seem to find the -mtune option for Intel Nehalem architectures (specifically Intel Xeon X5570). I was recommended -mtune=barcelona, but I got an error when compiling that. The closest is -mtune=nocona, which I believe is for the Core2 chips.
>
> Are there any mtune options for Intel Nehalem (for any version of GCC)?
>
>    
Do you mean you want to use an old version of gcc, issued prior to the 
advent of -mtune=barcelona?  That would reduce your performance 
potential for vectorized code.  It should be obvious, as Nehalem came 
later than Barcelona, that there would be no optimization for Nehalem in 
older versions.
You would have to experiment yourself to see whether -mtune=nocona helps 
performance in your case.  It's certainly not feasible to give you 
recommendations covering all old gcc versions, even if we could guess 
the other factors of your case.


-- 
Tim Prince

-mtune option for Intel Nehalem

[Rayne]

Hi all,

I can't seem to find the -mtune option for Intel Nehalem architectures (specifically Intel Xeon X5570). I was recommended -mtune=barcelona, but I got an error when compiling that. The closest is -mtune=nocona, which I believe is for the Core2 chips.

Are there any mtune options for Intel Nehalem (for any version of GCC)?

Thank you.

Regards,
Rayne