Any pretence at real life must handle concurrency somehow. From independent hardware components combined. Coordination: successfully sharing resources. Resources like files, shared memory, clip boards, and so on. concurrency problems. Hence boss thread must be kept efficient. philosophers, and santa claus. What if the processing you wish to perform with mutual exclusion needs to occur under certain conditions? However, process concurrency is non-atomic. They can get to santa as quickly as possible. Time for context switch in If Joe mows the lawn in an hour, Joe and Fred together should mow the Placing work in queue The alternative to concurrency is sequential execution. Concurrency is a property of the real world, and makes it practical. - pool of workers If all nine reindeer awaken him, santa delivers toys. synchronization. - + boss doesn't need to know details about workers Santa always eventually goes back to sleep. Quality of Service management, Advantages: The cost of getting it right can severely cut into the benefits. sensors). Better locality Synchronization requires OS mechanisms to control process execution. In the pipeline solution, each of 6 stages take 20 ms. How long will it take for these solutions to complete 10 toy orders and 11 toy orders? Provide mechanisms so processes can control concurrency. Concurrency is a property of the real world, and makes it practical. Although fanciful, these problems represent some fundamental Exploit concurrency within the OS to provide better performance. In pipeline 6 threads are equally used. Benefits to both applications and OS code, threads working on behalf of applications, OS level services like daemons and drivers. Event Driven model requires less memory than Boss-workers/Pipeline model, where the extra memory is required for helper thread for concurrent blocking I/O not for all concurrent requests. This page last modified on 2012 January 30. Time for context switch in threads is less, since memory is shared, hence mapping is not required between virtual and physical memory. To the extent that concurrency was a property of the hardware it was up to the kernel to control it. A philosopher either eats or thinks, always alternating between the two The two main forms of concurrency problems are. Specialization An OS shares resources with itself, requiring self-synchronization. Concurrency is the execution of the multiple instruction sequences at the same time. lawn in half an hour. Synchronization solutions can be used to provide coordination Throughput of system is limited by boss thread. Many philosophical (and physical) questions, all ignored. Operating (and hardware) systems are swimming in concurrency. Thus we have to execute the Consumer thread only under a certain condition (here- when the list becomes empty, print items). Sequential execution is inefficient and annoying. Efficiency => lower memory requirement & cheaper IPC 4. 1. PCB is divided into multiple data structures classified as follows: Handled in specific ways Therefore multithreading can be used to hide latency. The whole system is embedded in the world (keyboards, other systems, design. Since asynchronous calls are not easily available, helpers can be used to implement the async call functionality: Saved and restored on each context switch, Save and Restore only what needs to change on context switch, User lever library need to only update portion of the state, Events generated externally by components other than CPU (I/O devices, timers, other CPUs), Events triggered by CPU and software running on it, Efficiency => lower memory requirement & cheaper IPC.


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