Operating system chapter 4

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Threads, SMP, and Microkernels Chapter 4 

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Process * Resource ownership - process includes a virtual address space to hold the process image ° Scheduling/execution- follows an execution path that may be interleaved with other processes * These two characteristics are treated independently by the operating system 

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Process ° Dispatching is referred to as a thread or lightweight process ° Resource of ownership is referred to as a process or task 

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Multithreading * Operating system supports multiple threads of execution within a single process * MS-DOS supports a single thread ° UNIX supports multiple user processes but only supports one thread per process ٠» Windows, Solaris, Linux, Mach, and OS/2 support multiple threads 4 

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Toe process joneprocess 000000 ‎ees‏ سه سدسمب سس م كا ‏۳ ‏عع م ةس 1 لد ساد ‎Threatperprees‏ ‎ 

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Process ° Have a virtual address space which holds the process image ° Protected access to processors, other processes, files, and I/O resources 

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Thread ° An execution state (running, ready, etc.) * Saved thread context when not running * Has an execution stack ° Some per-thread static storage for local variables * Access to the memory and resources of its process ~ all threads of a process share this 

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Figure 4.2. Single Threaded and Multithreaded Process Models 

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Benefits of Threads Takes less time to create a new thread than a process Less time to terminate a thread than a process Less time to switch between two threads within the same process Since threads within the same process share memory and files, they can communicate with each other without invoking the kernel 

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Uses 01 111۲6005 1۳ 2 Single-User DROS reser work ° Asynchronous processing ° Speed of execution ° Modular program structure 

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Threads ° Suspending a process involves suspending all threads of the process since all threads share the same address space ° Termination of a process, terminates all threads within the process 

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Thread States ° States associated with a change in thread state - Spawn * Spawn another thread ~ Block ~ Unblock ~ Finish * Deallocate register context and stacks 

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Remote Procedure Call Using Single Thread 

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Remote Procedure Call Using Threads Figure 43 Remote Procedure Cull (RPC) Using Threads 

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Multithreading Figure 4.4 Multithreading Example on a Uniprocessor 

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Adobe PageMaker 

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User-Level Threads ° All thread management is done by the application ¢ The kernel is not aware of the existence of threads 

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User-Level Threads 

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19 

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Kernel-Level Threads ° Windows is an example of this approach ° Kernel maintains context information for the process and the threads ° Scheduling is done on a thread basis 

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Kernel-Level Threads 

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VAX Running UNIX-Like Operating System Table 4.1 Thread and Process Operation Latencies (Hs) [ANDE92] Kernel Level Operation __User-Lovel Threads Threads Processes Nall Fork 34 948 11,300 Signal Wait 37 441 1.840 

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Combined Approaches ° Example is Solaris ° Thread creation done in the user space ° Bulk of scheduling and synchronization of threads within application 

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Combined Approaches 

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Relationship Between Threads and Processes Tablo 4.2 Relationship Between Threads and Processes Description Example Systems 1 Each thread of execution isa Traditional UNIS ‘unique process with its owa implementations address space and resources ML Avprocess defines an address Windows NT. Solis, Limus space and dymamic resource OS2, OS/390, MACH ‘ownership. Multiple threads may be created and executed ‘within that process. LM Attuead may migrate from Ra (Clouds), Emerald fone process environment to smother. This allows a thread tobe easily moved among distinct systems. ‘MN Combines attributes of ‏ان‎ ‎and LM cases 

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Categories of Computer Systems ° Single Instruction Single Data (SISD) stream ~ Single processor executes a single instruction stream to operate on data stored in a single memory ° Single Instruction Multiple Data (SIMD) stream ~ Each instruction is executed on a different set of data by the different processors 

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Categories of Computer Systems * Multiple Instruction Single Data (MISD) stream ~ A sequence of data is transmitted to a set of processors, each of which executes a different instruction sequence. Never implemented ° Multiple Instruction Multiple Data (MIMD) ~ Aset of processors simultaneously execute different instruction sequences on different data sets 27 

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sIMD MIMD (single instruction (multiple instruction multiple data stream) multiple data stream) Shared-Memory Distributed-Memory (tightly coupled) (loosely coupled) Master/Slave Clusters ‘Multiprocessors (SMP) Figure 48 Parallel Processor Architectures 28 

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Symmetric Multiprocessing ° Kernel can execute on any processor ° Typically each processor does self-scheduling form the pool of available process or threads 

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30 موی [rica Procesor Processor 17 1 Sytem Bus 10 و 10 Adapter 10 ند mmetric Multiprocessor Organization vo ‘Subsystem Figure 49 

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011111111021 0065501 Operating System sign n Considerations a neous concurrent processes or threads ° Scheduling ° Synchronization ° Memory management ° Reliability and fault tolerance 

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Microkernels * Small operating system core * Contains only essential core operating systems functions * Many services traditionally included in the operating system are now external subsystems ~ Device drivers ~ File systems ~ Virtual memory manager ~ Windowing system ~ Security services 32 

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33 Pron (0) Mlerokernet Interprocess Communication ‏نا‎ ‎1 an Device Manage Kernel Prive Process Management Kern (a) Layered kernel Figure 4.10 Kernel Architecture user Mode Kernel Mae 

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261161115 01 2 Microkernel ۰ ‏هنن‎ made by a process ~ Don’t distinguish between kernel-level and user-level services - All services are provided by means of message passing ° Extensibility ~ Allows the addition of new services ° Flexibility ~ New features added ~ Existing features can be subtracted 34 

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261161115 01 2 Microkernel خم ۲ ~ Changes needed to port the system to a new processor is changed in the microkernel - not in the other services ° Reliability ~ Modular design ~ Small microkernel can be rigorously tested 

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Benefits of Microkernel Organization ° Distributed system support ~ Message are sent without knowing what the target machine is ° Object-oriented operating system - Components are objects with clearly defined interfaces that can be interconnected to form software 

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Microkernel Design * Low-level memory management ~ Mapping each virtual page to a physical page frame Figure 4.11 Page Fault Processing 37 

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Microkernel Design ° Interprocess communication ° I/O and interrupt management 

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Windows Processes ° Implemented as objects ° An executable process may contain one or more threads ° Both processes and thread objects have built-in synchronization capabilities 

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40 م ص ‎irtual address descriptors‏ ‎Handle Vable Available‏ objects Process ‘object ان اسر Handles Figure 4.12 A Windows Process and Its Resources 

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Windows Process Object 

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Windows Thread Object ‘Thread 3 ‘Tiree context ‏لإا سر‎ ts pity Tirta pocessrafinty ‘Tirta exeution Ene Alen sis Suspension count ‏ممما هه‎ ‘Termini port ‘Tire exit sis ‘Gate nea ‘Open teat (Quety treed snformation Settad information (Caren hea! ‏مس و‎ ادن ان Suspend Rene مت سیم ۳ (0) Thread object 42 ject type (one Beaty 

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Windows 2000 Thread States ° Ready ° Standby ° Running ° Waiting ° Transition ° Terminated 

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44 تست eS يي رست اعمط ‎Suspend,‏ ‘siting ١ Figure 4.14 Windows Thread States E> Resource Not Available Not Runnable 

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Solaris ° Process includes the user’s address space, stack, and process control block ° User-level threads ° Lightweight processes (LWP) ° Kernel threads 

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سح [ج] تن یدای ‎ert eat‏ )3( تسس Figure 4.15 Solaris Multithreaded Architecture Example 

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UNIX Process Structure Solaris Process Structure ‘peepee Figure 4.16 Process Structure in Traditional UNIX and Solaris [LEWI96] 47 

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Solaris Lightweight Data Structure Identifier Priority Signal mask Saved values of user-level registers Kernel stack Resource usage and profiling data Pointer to the corresponding kernel thread Pointer to the process structure 

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49 3 User-Level Threads هس هه ‎or Preamps‏ wakeup locked Lightweight Processes is User-Level Thread and LWP States ure 417 Si 

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Linux Task Data Structure State Scheduling information Identifiers Interprocess communication Links Times and timers File system Address space Processor-specific context 

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Linux States of a Process ° Running ° Interruptable ° Uninterruptable ° Stopped ° Zombie 

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52 Figure 4.18 Linux Process/Thread Model creation