【導(dǎo)讀】動，則地址綁定要延遲到運(yùn)行時。需要硬件對地址映射的支持，例如基。個不同的階段發(fā)生。更好的內(nèi)存空間利用率；沒有被使用的例程不被載入。事情時是非常有用的。內(nèi)存中的庫程序。theroutine.（存根用例程地址來替換自己，以及執(zhí)行例程。構(gòu)的程序設(shè)計很復(fù)雜。正確內(nèi)存管理的中心。

　　

【正文】 （ 共享的段） – same segment number （ 同樣的段號） ? Allocation.（ 分配） – first fit/best fit（ 首先 /最佳適配） – external fragmentation（ 外碎片） Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Segmentation Architecture (Cont.) ? Protection. With each entry in segment table associate（ 保護(hù)，每個段表的表項(xiàng)有） : – validation bit（ 有效位） = 0 ? illegal segment – read/write/execute privileges（ 讀 /寫 /執(zhí)行權(quán)利） ? Protection bits associated with segments。 code sharing occurs at segment level.（ 保護(hù)位同段相聯(lián)系，在段的級別進(jìn)行代碼共享。） ? Since segments vary in length, memory allocation is a dynamic storageallocation problem.（ 由于段的各個長度不同，內(nèi)存分配是一個動態(tài)存儲 分配問題。） ? A segmentation example is shown in the following diagram（下面的是一個段的例子） Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Segmentation with Paging – MULTICS ? The MULTICS system solved problems of external fragmentation and lengthy search times by paging the segments.（ MULTICS系統(tǒng)通過結(jié)合分頁解決外碎片問題和搜索時間長的問題。） ? Solution differs from pure segmentation in that the segmenttable entry contains not the base address of the segment, but rather the base address of a page table for this segment.（ 由于段表表項(xiàng)包含的不是“部分”的基址，而是這個“部分”一個頁表的基址，解決的辦法與純段不同。） Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts MULTICS Address Translation Scheme Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Segmentation with Paging – Intel 386 ? As shown in the following diagram, the Intel 386 uses segmentation with paging for memory management with a twolevel paging scheme.（ 如下圖所示， Intel 386使用段頁結(jié)合來進(jìn)行二級分頁的內(nèi)存管理。） Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Comparing MemoryManagement Strategies ? Hardware support（ 硬件支持） ? Performance（ 執(zhí)行） ? Fragmentation（ 碎片） ? Relocation（ 重定位） ? Swapping （ 交換） ? Sharing （ 共享） ? Protection（ 保護(hù)） Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts Silberschatz, Galvin, and Gagne ?1999 Applied Operating System Concepts