OS Linux case Studey

2. Development begins in 1991.

3. Ideas taken from MINIX.

4. 9300 LOC of C & 950 LOC of Assembly

5. Linux 2.0 issued in 1996 support 64 bit Architecture.

6. Two different GUI (GNOME & KDE) for Linux.

7. In early days, Linux development revolved around central OS kernel.

8. Linux kernel:

9. Is an entirely original piece of SW developed from scratch by the Linux community.

10. Linux system:

11. Some written from scratch, other borrowed from other development projects and other created in collection with other team.

12. Linux Distribution:

14. The first version was written by ken Thompson in assembler for the PDP-7 minicomputer

15. This was soon followed by a version for the PDP-11 written in a new language call C that was devised and implemented by Dennis Ritchie

17. Unix are open source OS

18. Use for educational purpose

20. Remaining 1 GB reserve for its Page Table and kernel data

21. 1 GB is not visible when running in user mode.

22. Linux also uses different linked lists of pages to facilitate an LRU-style algorithm.

23. Linux divides physical memory into three "zones:" one for DMA (devices I/0) pages, one for normal pages, and one for dynamically allocated memory.

24. Pages move between "hot," "cold," and "free" lists.

25. Frequently accessed pages will be on the "hot" list. Free pages will be on the "cold" or "free" list

27. First policy algorithm decides which pages to write out to disk, and when to write them.

28. Second the paging mechanism carries out the transfer and pages data back into physical memory when they are needed again.

29. Linux policy uses modified version of the standard clock (or second chance) algorithm.

30. Under Linux a clock is used, and every page has an age that is adjusted on each pass of the clock. Age is measure of youthfulness of pages.

31. LRU policy used.

32. Linux paging mechanism use swapping and partitions.

33. Swapping is slower due to the extra overhead.