Multitasking Systems: Difference between revisions
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Sketch on a papersheet the memory of the machine, with the pid_table, the two stacks , the current_pid variable, and then go. You should be able to emulate the |
Sketch on a papersheet the memory of the machine, with the pid_table, the two stacks , the current_pid variable, and then go. You should be able to emulate the behavior of that machine if --say-- you have a interrupt every 10+some_number_you_get_by_rolling_a_dice machine instructions. |
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And you'll see it can continue working on program 1 after it has been interrupted for 10+ instructions by program 2. |
And you'll see it can continue working on program 1 after it has been interrupted for 10+ instructions by program 2. |
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Of course "10+dice" is not enough to get decent performances. On modern systems, your timeslice is usually of a few milliseconds, which makes millions of instructions! Moreover, you don't always switch when the timer arise (because you might want the system clock more accurate than the switching rate) and you can switch on other events (e.g. because a program needs to wait for something or because something important like the end of a disk request happened). |
Of course "10+dice" is not enough to get decent performances. On modern systems, your timeslice is usually of a few milliseconds, which makes millions of instructions! Moreover, you don't always switch when the timer arise (because you might want the system clock more accurate than the switching rate) and you can switch on other events (e.g. because a program needs to wait for something or because something important like the end of a disk request happened). |
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== |
==See Also== |
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===Articles=== |
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*[[Context Switching]] |
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*[[Monotasking Systems]] |
*[[Monotasking Systems]] |
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*[[wikipedia:Computer_multitasking|Wikipedia - Computer Multitasking]] |
*[[wikipedia:Computer_multitasking|Wikipedia - Computer Multitasking]] |
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== |
==Threads== |
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*[[Topic: |
*[[Topic:9669|Designing a kernel to be preemptible]] |
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*[[Topic:812|Making a fully preemptible kernel]] |
*[[Topic:812|Making a fully preemptible kernel]] |
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