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1/13/16 CSE30341 Opera+ngSystemPrinciples Lecture2–Introduc5on–Con5nued Recap–LastLecture • Whatisanopera+ngsystem&kernel? • Whatisaninterrupt? CSE30341–Opera+ngSystemPrinciples 2 1 1/13/16 OS-Kernel CSE30341–Opera+ngSystemPrinciples 3 OS-Kernel CSE30341–Opera+ngSystemPrinciples 4 2 1/13/16 SystemArchitecture CSE30341–Opera+ngSystemPrinciples 5 Interrupt CSE30341–Opera+ngSystemPrinciples 6 3 1/13/16 Interrupt CSE30341–Opera+ngSystemPrinciples 7 Interrupt CSE30341–Opera+ngSystemPrinciples 8 4 1/13/16 Input/Output–I/O • Communica+onbetweenCPUand“outside world”: – Storage – Network – Keyboard/mouse – Display – Printer – … CSE30341–Opera+ngSystemPrinciples 9 Input/Output–I/O CSE30341–Opera+ngSystemPrinciples 10 5 1/13/16 Interac+ngwithI/O • System-controlled: – “Writethischunkofdatatoblock8,783,486” – “Pleasegivemethedatafromblocks7,345,286– 7,345,289” • Externalevents(systemreacts): – Theuserispressingtheshi_key – Block3,285,001appearstobebad – Dataarrivedoveranetworkconnec+on CSE30341–Opera+ngSystemPrinciples 11 Interac+ngwithI/O • Responsibili+esofOS: – Hide peculiarities of hardware devices from the user – Manage hardware devices (“resources”) efficiently – Prevent intentional/unintentional misuse CSE30341–Opera+ngSystemPrinciples 12 6 1/13/16 Interac+ngwithI/O • Application requests I/O from OS – Uses specific interface: system calls – Blocking: application will wait until I/O complete – Non-blocking: application will do something else in the meantime (and receive notification from OS when I/O complete) CSE30341–Opera+ngSystemPrinciples 13 Direct Memory Access (DMA) • CPUresponsiblefordatamovingto/fromI/Odevices • Alterna+ve:letaseparatecontrollerdoit(DMA) CSE30341–Opera+ngSystemPrinciples 14 7 1/13/16 DMAController I/O DeviceD6 Memory CPU Pleasecopy500bytes ofdatafromD6tomemory loca+on0x8570000and interruptmewhenyouare done DMA Controller vs. ReadfromD6 WritetoMemory ReadfromD6 WritetoMemory …. CSE30341–Opera+ngSystemPrinciples 15 Storage Structure • Main memory – only large storage media that the CPU can access directly – Random access memory – Volatile • Secondary storage – extension of main memory that provides large nonvolatile storage capacity – Magnetic disks – rigid metal or glass platters covered with magnetic recording material • Disk surface - tracks, subdivided into sectors • The disk controller determines the logical interaction between the device and the computer – Solid-state disks – faster than magnetic disks, nonvolatile • Various technologies • Becoming more popular CSE30341–Opera+ngSystemPrinciples 16 8 1/13/16 Storage-Device Hierarchy registers cache main memory solid-state disk magnetic disk optical disk magnetic tapes CSE30341–Opera+ngSystemPrinciples 17 Storage Hierarchy • Storage systems organized in hierarchy – Size – Speed – Cost – Volatility • Caching – leverage faster storage system; higher layer can be cache for lower layer CSE30341–Opera+ngSystemPrinciples 18 9 1/13/16 Caching • One of the most important principles in systems • Information in use copied from slower to faster storage temporarily • Faster storage (cache) checked first to determine if information is there – If it is, information used directly from the cache (fast) – If not, data copied to cache and used there • Cache smaller than storage being cached – Cache management important design problem – Cache size and replacement policy CSE30341–Opera+ngSystemPrinciples 19 Computer-System Architecture • General-purpose processors (CPU) versus special-purpose processors (controllers) • Multiprocessor systems are now typical – Parallel systems, tightly-coupled systems – Advantages include: 1. Increased throughput 2. Economy of scale 3. Increased reliability – graceful degradation or fault tolerance CSE30341–Opera+ngSystemPrinciples 20 10 1/13/16 Symmetric Multiprocessing (SMP) Architecture UMA–UniformMemoryAccess • Allsharethesamememoryonthesamemachine,samecosttoaccess. • Mayhaveaprivatecache NUMA–Non-uniformMemoryAccess • Eachprocessorhasitsownmemory CSE30341–Opera+ngSystemPrinciples 21 Multi-Core Design • Multiple “cores” on same chip – On-chip communication is fast – Power consumption can be reduced CSE30341–Opera+ngSystemPrinciples 22 11 1/13/16 Clustered Systems • Like multiprocessor systems, but multiple systems working together – Connected via LAN (local-area network) – Storage often shared via SAN (storage-area network) – Main reasons: • High availability – Asymmetric clustering (one machine in hot-standby mode) – Symmetric clustering (multiple machines running and monitoring each other) • High performance (HPC) – Applications must be written to exploit parallelization CSE30341–Opera+ngSystemPrinciples 23 Clustered Systems computer interconnect computer interconnect computer storage area network CSE30341–Opera+ngSystemPrinciples 24 12 1/13/16 Operating Systems Concepts A von Neumann architecture CSE30341–Opera+ngSystemPrinciples 25 Opera+ngSystemsConcepts • Mul5programming(efficiency) – SingleusercannotkeepCPUandI/Odevicesbusy atall+mes – Jobs(code&data)organizeds.t.CPUalwayshas atleastonetoexecute – Subsetofjobskeptinmemory – Whenajobhastowait(e.g.,forI/O),theOS switchestoanotherjob CSE30341–Opera+ngSystemPrinciples 26 13 1/13/16 Memory Layout for Multiprogrammed System CSE30341–Opera+ngSystemPrinciples 27 Opera+ngSystemsConcepts • Timesharing(mul5tasking): – Switchingbetweenjobshappenssofrequentlythat userscaninteractwitheachjobwhileitisrunning: interac5vecompu5ng – Response5me(e.g.,<1second) – Eachuserhasatleast1programexecu+nginmemory (process) – Ifseveraljobsreadytorunatthesame+me:CPU scheduling – Ifprocessesdon’tfitintomemory:swapping – Virtualmemoryallowsofexecu+onofpar+ally loadedprocesses CSE30341–Opera+ngSystemPrinciples 28 14 1/13/16 Opera+ngSystemsConcepts • Accesstoresourcesneedstobecontrolled: – Simultaneousaccess – Unauthorizedaccess – “Improper”access(e.g.,toolong) • Dual-modeopera5ngsystems – Usermode(applica+on) – Kernelmode(OSandprivilegedinstruc+ons) – Modebitindicatescurrentmode(0=kernel) – Transi+onviasystemcalls CSE30341–Opera+ngSystemPrinciples 29 From User to Kernel Mode • Timer to prevent infinite loop / process hogging resources – – – – Set interrupt after specific period Operating system decrements counter When counter zero generate an interrupt Set up before scheduling process to regain control or terminate program that exceeds allotted time CSE30341–Opera+ngSystemPrinciples 30 15 1/13/16 ProcessManagement • Process=programinexecu+on! – Program=passive – Process=ac+ve • Processneedsresources(CPU,memory,I/O, ini+aliza+ondata,files,etc.) • Single-threadedprocess:oneprogram counter(PC) • Mul5-threadedprocess:oneprogramcounter perthread CSE30341–Opera+ngSystemPrinciples 31 Process Management Activities The operating system is responsible for the following activities in connection with process management: • • • • • Creating and deleting both user and system processes Suspending and resuming processes Providing mechanisms for process synchronization Providing mechanisms for process communication Providing mechanisms for deadlock handling CSE30341–Opera+ngSystemPrinciples 32 16 1/13/16 Memory Management • All data in memory before and after processing • All instructions in memory in order to execute • Memory management determines what is in memory and when – Optimizing CPU utilization and computer response to users • Memory management activities – Keeping track of which parts of memory are currently being used and by whom – Deciding which processes (or parts thereof) and data to move into and out of memory – Allocating and de-allocating memory space as needed CSE30341–Opera+ngSystemPrinciples 33 Storage Management • OS provides uniform, logical view of information storage – Abstracts physical properties to logical storage unit - file – Each medium is controlled by device (i.e., disk drive, tape drive) • Varying properties include access speed, capacity, data-transfer rate, access method (sequential or random) • File-System management – Files usually organized into directories – Access control on most systems to determine who can access what – OS activities include • • • • Creating and deleting files and directories Primitives to manipulate files and directories Mapping files onto secondary storage Backup files onto stable (non-volatile) storage media CSE30341–Opera+ngSystemPrinciples 34 17 1/13/16 Mass-Storage Management • Usually disks used to store data that does not fit in main memory or data that must be kept for a “long” period of time • Proper management is of central importance • Entire speed of computer operation hinges on disk subsystem and its algorithms • OS activities – Free-space management – Storage allocation – Disk scheduling • Some storage need not be fast – Tertiary storage includes optical storage, magnetic tape – Still must be managed – by OS or applications – Varies between WORM (write-once, read-many-times) and RW (read-write) CSE30341–Opera+ngSystemPrinciples 35 Performance of Various Levels of Storage Level 1 2 3 4 5 Name registers cache main memory solid state disk magnetic disk Typical size < 1 KB < 16MB < 64GB < 1 TB < 10 TB Implementation technology custom memory on-chip or off-chip with multiple CMOS SRAM ports CMOS CMOS SRAM flash memory magnetic disk Access time (ns) 0.25 - 0.5 80 - 250 25,000 - 50,000 5,000,000 Bandwidth (MB/sec) 20,000 - 100,000 5,000 - 10,000 1,000 - 5,000 500 20 - 150 Managed by compiler 0.5 - 25 hardware operating system operating system operating system disk or tape disk main memory disk cache Backed by • Movementbetweenlevelsofstoragehierarchycanbe explicitorimplicit CSE30341–Opera+ngSystemPrinciples 36 18 1/13/16 Protection and Security • Protection – any mechanism for controlling access of processes or users to resources defined by the OS • Security – defense of the system against internal and external attacks CSE30341–Opera+ngSystemPrinciples 37 Recap • KeyPoints – WhatisDMA? – Whatisthememoryhierarchy? – Whatiscaching? – Whatisvirtualmemory? – WhatisaSAN? – Whatisthedifferencebetweenkernelanduser mode? CSE30341–Opera+ngSystemPrinciples 38 19