Messages in this thread | | | From | "M. Edward Borasky" <> | Subject | RE: i686 SMP systems with more then 12 GB ram with 2.4.x kernel ? | Date | Tue, 1 Jan 2002 10:15:59 -0800 |
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> Because much of the memory cannot be used for kernel objects there is an > imbalance in available resources and its very hard to balance them sanely.
As I understand it, in a Linux / i686 system, there are three zones: DMA (0 - 2^24-1), low (2^24 - 2^30-1) and high (2^30 and up). And the hardware (PAE) apparently distinguishes memory addresses above 2^32-1 as well. Questions:
1. Shouldn't there be *four* zones: (DMA, low, high and PAE)?
2. Isn't the boundary at 2^30 really irrelevant and the three "correct" zones are (0 - 2^24-1), (2^24 - 2^32-1) and (2^32 - 2^36-1)?
3. On a system without ISA DMA devices, can DMA and low be merged into a single zone?
4. It's pretty obvious exactly which functions require memory under 2^24 -- ISA DMA. But exactly which functions require memory under 2^30 and which functions require memory under 2^32? It seems relatively easy to write a Perl script to truck through the kernel source and figure this out; has anyone done it? It would seem to me a valuable piece of information -- what the demands are for the relatively precious areas of memory under 1 GB and under 4 GB. -- M. Edward Borasky
znmeb@borasky-research.net http://www.borasky-research.net
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