现代操作系统全套配套课件4eTanenbaumPPT及教学资料Chapter03-Memory Management.ppt

Segmentation with Paging: The Intel x86 (2) Figure 3-39. x86 code segment descriptor. Data segments differ slightly. Tanenbaum Bo,Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Segmentation with Paging: The Intel x86 (3) Figure 3-40. Conversion of a (selector, offset) pair to a linear address. Tanenbaum Bo,Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Segmentation with Paging: The Intel x86 (4) Figure 3-41. Mapping of a linear address onto a physical address. Tanenbaum Bo,Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. End Chapter 3 Tanenbaum Bo,Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Not Recently Used Algorithm At page fault, system inspects pages Categories of pages based on the current values of their R and M bits: Class 0: not referenced, not modified. Class 1: not referenced, modified. Class 2: referenced, not modified. Class 3: referenced, modified. Tanenbaum Bo,Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Second-Chance Algorithm Figure 3-15. Operation of second chance. (a) Pages sorted in FIFO order. (b) Page list if a page fault occurs at time 20 and A has its R bit set. The numbers above the pages are their load times. Tanenbaum Bo,Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Clock Page Replacement Algorithm Figure 3-16. The clock page replacement algorithm. Tanenbaum Bo,Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Simulating LRU in Software Figure 3-17. The aging algorithm simulates LRU in software. Shown are six pages for five clock ticks. The five clock ticks are represented by (a) to (e). Tanenbaum Bo,Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Working Set Algorithm (1) Figure 3-18. The working set is the set of pages