CS4500/5500 Operating Systems Computer and Operating Systems Overview

Transcription

1 Operating Systems Cmputer and Operating Systems Overview Yanyan Zhuang Department f Cmputer Science UC. Clrad Springs Ref. MOS4E, OS@Austin, Clumbia, UWisc

2 Overview Recap f last class What is an perating system? Functinalities f perating systems Types f perating systems Cmputer hardware review Operating system rganizatin 2 Ref. MOS4E, OS@Austin, Clumbia, UWisc

3 Cmputer Hardware Review Basic cmpnents f a simple persnal cmputer CPU: data prcessing Memry: vlatile data strage Disk: persistent data strage NIC: inter-machine cmmunicatin Bus: intra-machine cmmunicatin 3 Ref. MOS4E, OS@Austin, Clumbia, UWisc

4 Central Prcessing Unit (CPU) Cmpnents Arithmetic Lgic Unit (ALU) Cntrl Unit (CU) Fetch, decde, execute Clck rate The speed at which a CPU is running Data strage: mem access slw General-purpse registers: EAX, EBX Special-purpse registers: PC, SP, 4 Ref. MOS4E, OS@Austin, Clumbia, UWisc

5 Multi-Cre Prcessrs Multiple CPUs n a single chip C Cache FSB DRAM Cntrller Memry Nn-unifrm perfrmance A schematic view f Intel Cre 2 5 Ref. MOS4E, OS@Austin, Clumbia, UWisc

6 Memry As fast as CPU, small High speed, limited size A typical memry hierarchy 6 Ref. MOS4E, OS@Austin, Clumbia, UWisc

7 Why Cache is imprtant? Whenever resurce can be divided int pieces, sme f which used much mre heavily than thers, caching is ften used t imprve perfrmance. A larger size than registers A much faster than RAM 7 Ref. MOS4E, OS@Austin, Clumbia, UWisc

8 Mre n CPU Cache Different types f cache L1 cache: inside CPU and feeds decded instructins int CPU s executin engine (n delay) L2 cache: inside r utside CPU, hlds megabytes f recently used memry wrds (1-2 clck cycles) L3 cache (LLC last level cache): utside CPU 8 Ref. MOS4E, OS@Austin, Clumbia, UWisc

9 Mre n CPU Cache Cache management When t put a new item int the cache Which item t remve frm the cache when a slt is needed Where t put a newly evicted item in the larger memry When t write dirty item back t memry 9 Ref. MOS4E, OS@Austin, Clumbia, UWisc

10 Memry Requests can t be satisfied by cache, g here Large size, 10^6x slwer A typical memry hierarchy than RAM 10 Ref. MOS4E, OS@Austin, Clumbia, UWisc

11 Memry Management Multiprgramming Accmmdate multiple prcesses in main memry Hw t prtect the prgrams frm ne anther and the kernel frm them all? Prcesses shuld nt reference memry lcatins in anther prcess withut permissin What if all prcesses memry requirement exceeds the physical memry? Virtual memry address ßà Physical memry address 11 Ref. MOS4E, OS@Austin, Clumbia, UWisc

12 Hard Disks Track Disk heads mve tgether Sectr A stack f platters, a surface with a magnetic cating Disk head: each side f a platter has separate disk head Each surface is divided int tracks and sectrs 500 t 2,000 tracks per surface 32 t 128 sectrs per track 12 Ref. MOS4E, OS@Austin, Clumbia, UWisc

13 Magnetic Disk Characteristics Read/write data is a three-stage prcess: Seek time: psitin the arm ver the prper track Rtatinal latency: wait fr the desired sectr t rtate under the read/write head Transfer time: transfer a blck f bits (sectr) under the read-write head Average seek time as reprted by the industry: Typically in the range f 8 ms t 15 ms Due t lcality f disk reference Lng seek time Only ne request at a time Actual average seek time may nly be 25% t 33% f the advertised number 13 Ref. MOS4E, OS@Austin, Clumbia, UWisc

14 I/O Devices Device cntrller T prvide a simple interface f device cntrl t OS Physically cntrls the device: accepts cmmands frm OS, and carries them ut Device driver The sftware that talks t a cntrller, giving it cmmands and accepting respnses 14 Ref. MOS4E, OS@Austin, Clumbia, UWisc

15 I/O Devices Device cntrller T prvide a simple interface f device cntrl t OS Physically cntrls the device: accepts cmmands frm OS, and carries them ut Device driver The sftware that talks t a cntrller, giving it cmmands and accepting respnses OS Every cntrller has a small number f registers: A disk cntrller might have registers fr specifying disk address, directin (r/w), etc. Device driver registers Device cntrller 15 Ref. MOS4E, OS@Austin, Clumbia, UWisc

16 Interactins between OS and I/O Devices The OS gives cmmands t the I/O devices The I/O device ntifies the OS when the I/O device has cmpleted an peratin r has encuntered an errr Data is transferred between memry and an I/O device 16 Ref. MOS4E, OS@Austin, Clumbia, UWisc

17 Hw I/O Devices Ntify the OS? Hardware device events Hardware devices prduce events at times and in patterns nt knwn in advance } Keybard presses } Incming netwrk packets } Muse mvements Hw t make infrmatin generated by these events available t running applicatins? Three methds: plling, interrupt, DMA 17 Ref. MOS4E, OS@Austin, Clumbia, UWisc

18 Hw I/O Devices Ntify the OS? Plling (busy waiting) The I/O device put infrmatin in a status register The OS peridically check the status register Simple design: OS peridically checks device Disadvantage: (1) Mst time device has n input data waste CPU time (2) High latency device input must wait fr plling interval 18 Ref. MOS4E, OS@Austin, Clumbia, UWisc

19 Hw I/O Devices Ntify the OS? Plling (busy waiting) The I/O device put infrmatin in a status register The OS peridically check the status register Interrupt Whenever an I/O device needs attentin frm the prcessr, it interrupts the prcessr frm what it is currently ding HW signals the OS when events ccur OS switches away frm running prcess, handle the event Mre respnsive than plling, but cmplex implementatin 19 Ref. MOS4E, OS@Austin, Clumbia, UWisc

20 Interrupts Interrupts An interruptin f the nrmal sequence f executin Imprves prcessing efficiency (cmpare t plling) Cmplex: a suspensin f a prcess caused by an external event, perfrmed in a way that the prcess can be resumed Types f interrupts I/O Timer 20 Ref. MOS4E, OS@Austin, Clumbia, UWisc

21 I/O Interrupt OS Device driver registers Device cntrller (a) 1. CPU writes cmds in t device registers 2. The device signals interrupt cntrller 3. Interrupt cntrller infrms CPU 4. CPU accepts the interrupt and triggers the service rutine (b) 21 Ref. MOS4E, OS@Austin, Clumbia, UWisc

22 I/O Interrupt (a) (b) 1. Save current instructin inf, switch t kernel mde 2. Find interrupt handler (service rutine) fr device 3. Interrupt handler finishes: return t user prgram 22 Ref. MOS4E, OS@Austin, Clumbia, UWisc

23 Hw I/O Devices Ntify the OS? Plling The I/O device put infrmatin in a status register The OS peridically check the status register Interrupt Whenever an I/O device needs attentin frm the prcessr, it interrupts the prcessr frm what it is currently ding DMA Direct memry access: delegate I/O respnsibility frm CPU (mre in Chapter 5) 23 Ref. MOS4E, OS@Austin, Clumbia, UWisc

24 System Calls Frm last class: transitin between user/kernel mde Interrupt HW device requests OS services Trap user prgram requests OS services: system calls } A user prgram needs a system service (reading a file): execute a trap instructin t transfer cntrl t OS } OS inspects parameters, carries ut system call, returns cntrl t the instructin fllwing the system call Exceptin errr handling 24 Ref. MOS4E, OS@Austin, Clumbia, UWisc

25 System Calls 1 3: calling prgram pushes paras n stack 4: calls the library prcedure 5: library prcedure puts system-call # in a register 6: library prcedure executes TRAP instructin: user mde à kernel mde There are 11 steps in making the system call read (fd, buffer, nbytes) 25 Ref. MOS4E, OS@Austin, Clumbia, UWisc

26 System Calls 7: kernel cde examines system-call #, dispatches t crrect system-call handler 8: the system-call handler runs 9: cntrl returned t user-space library prcedure at the instructin fllwing TRAP 10: library prcedure returns t user prgram 11: user prgram cleans up stack There are 11 steps in making the system call read (fd, buffer, nbytes) 26 Ref. MOS4E, OS@Austin, Clumbia, UWisc

27 System Calls What is the key difference between interrupts and traps (system calls)? prgram-triggered vs. event-triggered synchrnus vs. asynchrnus There are 11 steps in making the system call read (fd, buffer, nbytes) 27 Ref. MOS4E, Clumbia, UWisc

28 Operating System Cmpnents Prcess management Memry management File and strage Netwrking 28 Ref. MOS4E, Clumbia, UWisc

29 Prcess Management (Chapter 2) Prcess: a fundamental OS cncept Memry address space Sme set f registers (prgram cunter, stack pinter) Prtectin dmain Resurce allcatin OS respnsibilities fr prcess management Prcess creatin and deletin Prcess scheduling, suspensin, and resumptin Inter-prcess cmmunicatin and synchrnizatin 29 Ref. MOS4E, OS@Austin, Clumbia, UWisc

30 Memry Management (Chapter 3) Memry A large array f addressable wrds and bytes OS respnsibilities fr memry management Allcate and de-allcate memry space Keep memry space efficiently utilized Keep track f which part f memry are used and by whm Design gals: transparency and efficiency 30 Ref. MOS4E, OS@Austin, Clumbia, UWisc

31 File and Strage Management (Chapter 4) A file is a cllectin f data (usually) stred n disk with a unique name Prgrams Data Devices (UNIX & Linux) OS respnsibilities fr file management Organize directries and files Map files nt disk OS respnsibilities fr disk management Disk space management Disk scheduling 31 Ref. MOS4E, OS@Austin, Clumbia, UWisc

32 Additinal Readings and Practice Sectin 1.6 and try the fllwing Linux cmmands } wh, uname, ls, cat, cp, rm, mv, cd, mkdir, tuch, chmd } Use man t see the manual f abve cmmends Write a C prgram with an utput t the screen } strace trace.txt./your_prog } See the system calls triggered (execve, write, ) } EAS datacenter tutrial 32 Ref. MOS4E, OS@Austin, Clumbia, UWisc

33 Summary Cmputer hardware Time-sharing: CPU Space-sharing: memry, disk OS cmpnents Prcess management Memry management File and strage management 33 Ref. MOS4E, Clumbia, UWisc