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Im using the EeeKernel [toofishes] and found out that it was built using a VM split of 2G/2G. It would be nice to have wine working so i was considering building the kernel with a more classic 3G/1G split. However I would like to know what kind of performance hit/benefit this would be associated with. The system that's in question is an Eeepc 1000 with 2GB of memory so the question is: isn't the split supposed to divide kernel memory from user? If the split is 2G/2G wouldn't that mean i need 4GB or is it just reserving 50% of addressing for the kernel alone. I'm assuming its the latter. Anyways i did a bit of googling and failed to find an explanation of the effects of these options.
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We all know that 32bit systems can address a maximum of 4GB. But Intel uses their famous (or infamous) flat memory model where in order to address hardware like your video card or your USB devices, there must be some bits reserved for those virtual addresses.
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| Addr register 32 bits|
|_________________|
...
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| Addr register |||||
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(with some bits used exclusively for kernel and device purposes)
The VM split options involve the limit on how many bits will be reserved for the kernel and how many will be left over for main memory addressing.
Now back to what I was trying to achieve, I ended up compiling the kernel with each of the options available. None of them ended up allowing me to address my full 2GB of memory while allowing wine to run. I ended up solving my problem by enabling an option called HIGHMEM4G which to the best of my knowledge uses a struct of more than a DWORD for virtual memory addressing. This would allow a machine with 4GB of memory to be able to address all of it and still be able to have addresses for hardware devices.
As for performance of the system depending on each option, I couldn't tell any difference but I would still love for someone to share some additional insight. (I'm pretty sure that HIGHMEM4G is the slowest one ^_^)
Last edited by coreboy (2009-02-22 19:35:13)
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