2009年4月8日 星期三

[Linux] High and low memory

Low memory
Memory for which logical addresses exist in kernel space. On almost every system you will likely encounter, all memory is low memory

High memory
Memory for which logical address do not exist, because it is beyond the address range set aside for kernel virtual addresses.

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ZONE

ZONE_DMA (0-16 MB) - 包含設定 ISA/PCI 裝置所需的較低實體記憶體區域的範圍
ZONE_NORMAL (16-896 MB) - 直接由 kernel 對映上層實體記憶體區域的範圍ZONE_HIGHMEM (896 MB 或更高) - 並未被 kernel 所對映的剩餘有效記憶體區域

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