【xv6學習之番外篇】記憶體管理
阿新 • • 發佈：2019-02-15
An approach to space management that provides even further simplification of space-management software is to maintain a one-to-one correspondence between segment descriptors
and page-directory entries, as Figure 5-13 illustrates. Each descriptor has a base address in which the low-order 22 bits are zero; in other words, the base address is mapped by the first entry of a page table. A segment may have any limit from 1 to 4 megabytes.
Depending on the limit, the segment is contained in from 1 to 1K page frames. A task is thus limited to 1K segments (a sufficient number for many applications), each containing up to 4 Mbytes. The descriptor, the corresponding page-directory entry, and the
corresponding page table can be allocated and deallocated simultaneously.