chap 08-2019F.pdf - Context Switching Chapter 8 Introduction Context switch When \u03bcC\/OS-III decides to run a different task it saves the current

chap 08-2019F.pdf - Context Switching Chapter 8...

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Context Switching Chapter 8
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Introduction } Context switch } When μ C/OS-III decides to run a different task, it saves the current task’s context, which typically consists of the CPU registers, onto the current task’s stack and restores the context of the new task and resumes execution of that task. } Context switching adds overhead. } The more registers a CPU has, the higher the overhead. } The time required to perform a context switch is generally determined by how many registers must be saved and restored by the CPU. } Two types of context switches } from a task } from an ISR. Fall 2018 Context Switching 2
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Introduction } A fictitious 32-bit CPU is assumed. } 16 registers, a separate ISR stack pointer, and a status register. Fall 2018 Context Switching 3 CPU register stacking order of ready task
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8-1 OSCtxSw() } OSCtxSw() is called when the task level scheduler ( OSSched() ) determines that a new high priority task needs to execute. Fall 2018 Context Switching 4
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  • Fall '19
  • kim

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