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Old 05-06-2008, 01:45 PM   #1
jjana123
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64-bit or 32-bit Application on 64-bit Linux


Hi All,

Will 64-bit Application running on 64-bit Linux perform better than 32-bit Application running on 64-bit Linux?

Appreaciate your input.

Thanks & Regards,
Joydeep

Last edited by jjana123; 05-06-2008 at 02:03 PM.
 
Old 05-06-2008, 01:55 PM   #2
TB0ne
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Quote:
Originally Posted by jjana123 View Post
Will 64-bit Application running on 64-bit Linux perform better than 64-bit Application running on 64-bit Linux?
I assume you meant a 32-bit application under 64 bit linux. Yes, it most probably will perform a bit slower than the 64/64 setup.
 
Old 05-06-2008, 02:06 PM   #3
jjana123
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Quote:
Originally Posted by TB0ne View Post
I assume you meant a 32-bit application under 64 bit linux. Yes, it most probably will perform a bit slower than the 64/64 setup.
Thanks for your reply.

Yes I meant "a 32-bit application under 64 bit linux".

What is the reason you say so? May be for heavy allication with lot of memory operation it make sense to make 64-bit application.

Thanks,
Joydeep
 
Old 05-06-2008, 04:02 PM   #4
TB0ne
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Originally Posted by jjana123 View Post
Yes I meant "a 32-bit application under 64 bit linux".

What is the reason you say so? May be for heavy allication with lot of memory operation it make sense to make 64-bit application.
Well, you didn't say what you were running, or what your desired result was. I was generalizing, but if your app can take advantage of the 64 bit address space (and the libraries, OS, and other parts can too), it'll probably run faster than a 32 bit app in a 64 bit space.

Unless you're seriously crunching things, though, I doubt you'd see a huge speed difference.
 
Old 05-06-2008, 06:27 PM   #5
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For most applications it will make no significant difference.

For lots of applications, a 32 bit version will be a little faster because 64 bit pointers are bigger and applications may store a lot of pointers resulting in more cache misses for the 64 bit version.

For some applications, the 64 bit version will be moderately faster because the 64 bit architecture has more registers and the GCC compiler is rather stupid about architectures that have too few registers and some code will be optimized badly for 32 bit because of that.

(As I recently overlooked in a similar thread) I think a few applications will run a lot faster in 64 bit because they can make good use of CPU features such as SSE. Those CPU features are also available in 32-bit mode, but probably aren't used by 32 bit binaries. I don't know whether the GCC compiler can't be made to use those features for 32-bit binaries or whether it can be made to but requiring some special action in source or build syntax that typically isn't there. Either way, the bottom line for an ordinary user of 32 bit executables is that those CPU features aren't used.

All of the above overlooks the direct benefits of 64 bit mode: much better support for 64 bit integers ("long long" data type in C++) as well as virtual addresses beyond 4GB. It think overlooking those is best because those direct benefits of 64 bit mode are probably even less used by ordinary applications, than special CPU features such as SSE.
 
  


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