Ubuntu 12.10: 32-bit vs. 64-bit Linux Performance

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Originally Posted by rgloor

If that is fanatics by your definition, then you might call me fanatic. ;)

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You're right, "enthusiasts" is more appropriate.

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Originally Posted by whitecat

Diego Elio Pettenò wrote:
The data is also coming from a synthetic test, not from an actual overall system usage, and if you have any clue about benchmarks you know that the numbers can easily lie out of their teeth!

And in your benchmark:
x86-64 : 114 %
x32 : 117 %

Awesome. A new ABI for that?
x32 has 9 years late. For desktop or servers nobody will use x32 because x86-64 is already here.

And you forgot that proprietary vendors (Nvidia, AMD, Adobe, Microsoft) will certainly never support x32 because it's a waste of time.

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The benchmark does not say x32: 117%
It says x32: 100% and x64:114%
So yes, a new ABI to gain 14% in execution time (and 40% in memory consumption, in the particular case).

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And you forgot that proprietary vendors (Nvidia, AMD, Adobe, Microsoft) will certainly never support x32

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Why do you think this to be a problem when the same blog talking about x32 "myths" you linked explicitely states:

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Also remember that for compatibility the syscalls are kept the same with x86-64

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Having the Linux kernel compiled with CONFIG_X86_X32 doesn't mean it will be limited to X32 binaries.
https://bugs.archlinux.org/task/31270

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Originally Posted by kokoko3k

The benchmark does not say x32: 117%
It says x32: 100% and x64:114%
So yes, a new ABI to gain 14% in execution time (and 40% in memory consumption, in the particular case).

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Sorry, I read it too fast.

Nevertheless, what is your g++ command-line to compile this bench?

While I know ubuntu isn't released in an X32 flavor yet, the better article would be a comparison of all 3, X32, x86 and x64.

whats the big deal with these pointers? is smaller pointers are good for performance, why not reduce them even further? would probably be an interesting thing when someday 128 bit may be introduced, to have a dynamic pointer size. if thats possible at all..

i blame either memory alignment or pointer arithmetic(if its not the same) for those couple slower tests
(compiler can too, but idk that)

64bit program with proper memory alignment should take twice as much memory then the 32bit counterpart (also with memory alignment)
what is not optimal for all things (space-time trade off)

64bit cpu should be faster in all ways (except memory consumption, but memory speed should be the same and 64bit can fetch 64bits at a time, 32bit can 32) when working in 64bit mode as you at least have extra registers to play with (not faster by much as the cpu has "register renaming" and some extra tricks in bout modes)

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Originally Posted by jakubo

whats the big deal with these pointers? is smaller pointers are good for performance, why not reduce them even further? would probably be an interesting thing when someday 128 bit may be introduced, to have a dynamic pointer size. if thats possible at all..

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there have been 64bit cpu's even 20 years ago, but have not been used for practical reasons
mind you can use the 128bit sse registers for storing data and processing floating points in bout 32 and 64bit modes (in 64bit mode you get extra sse registers, same applies as above stated)


http://www.cs.umd.edu/class/sum2003/...p/pointer.html
about pointer arithmetic

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Originally Posted by jakubo

would probably be an interesting thing when someday 128 bit may be introduced, to have a dynamic pointer size.

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AMD64 arch can theoretically handles up to 4 millions GB of RAM.
So... it's too early to think about an Athlon 128.