how can I get the ZONE_DMA size ??

[RS]

Hello
    I learned that the ZONE_DMA size is 16MB from the book KDE, but on my laptop the ZONE_SIZE is maybe 12M. I print the page directory informations, and from the NO.768 to NO.770 pte is not direct mapping until the NO.771 pte.
    So, how can I get the ZONE_DMA real size ? Is there any kernel functions or configuration files ? I want to get the accurate number.


Thanks,
HeChuan
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