These multi core cpus look to the operating system

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" These multi-core CPUs look to the operating system just as N standard processors.
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Introduction to OS 19 37 Computer System Architecture (cont’d) ! Clustered Systems : " Clustered computers share storage and are linked via a local-area network (LAN). " Differ from multiprocessor systems in that they are composed of two or more individual system coupled together. " Goal : to provide high-availability service. # Service will continue even if one or more systems in the cluster fail. # A layer of cluster software runs on the cluster nodes. $ Each node can monitor one or more of the others (over the LAN). $ If the monitored machine fails, the monitoring machine can take over the failed machine. 38 Computer System Architecture (cont’d) " Clustering can be structured asymmetrically or symmetrically . " Asymmetric clustering : # One machine is in hot-standby mode, does nothing but monitor the active nodes . # If an active fails, the hot-standby host becomes the active node. " Symmetric mode : # Host are monitoring each other. # More efficient as it uses all of the available hardware.
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Introduction to OS 20 39 Operating System Structure ! Operating systems vary greatly in their makeup, since they are organized along many different lines. " However, there are many commonalities. ! One of the most important aspect of operating systems is the ability to multiprogramming . " User cannot keep CPU and I/O devices busy at all times. # Jobs have to wait for some task, such as an I/O operation, to complete. # The CPU would sit idle. " Multiprogramming organizes jobs so CPU always has one to execute . 40 Operating System Structure (cont’d) ! Multiprogramming : " A subset of total jobs in system is kept in memory. " One job is selected and run. " When it has to wait (for I/O for example) , OS switches to another job. " When that job needs to wait, the CPU is switched to another job, and so on. " Eventually, the first job finishes waiting and gets the CPU back. " As long as at least one job needs to execute, the CPU is never idle .
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Introduction to OS 21 41 Operating System Structure (cont’d) 42 Operating System Structure (cont’d) ! Time sharing (multitasking): " Is logical extension of multiprogramming . " CPU switches jobs frequently . ! Time sharing is frequently used in interactive computer system . " For example, windows systems, which provide direct communication between the user and the system (using keyboard or mouse). # The response time (of each job) should be short!! " The operating system must switch rapidly from one job (for one user) to next, such that each user is given the impression that the entire computer system is dedicated to his use.
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Introduction to OS 22 43 Operating System Structure (cont’d) ! Time sharing and multiprogramming require several jobs to be kept simultaneously in memory. " A program loaded into memory and executing is called a process . ! Since main memory is too small to accommodate all jobs, the jobs are kept initially on the disk in the job pool .
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  • Spring '12
  • GwangS.Jung
  • OS, main memory

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