The scheduler maintains a queue of executable threads for each priority level. These are known as ready threads. When a processor becomes available, the system performs a context switch. The steps in a context switch are:
Save the context of the thread that just finished executing.
Place the thread that just finished executing at the end of the queue for its priority.
Find the highest priority queue that contains ready threads.
Remove the thread at the head of the queue, load its context, and execute it.
Step 3: Verify Context Close the original cmd window as seen in Figure 2 and check Task Manager (Task Manager can be launched by right-clicking the taskbar and choosing Task Manager)(Explain how you launch task manager) to ensure your command window is now running in System context.
Context Switches.; 2 minutes to read; In this article. The scheduler maintains a queue of executable threads for each priority level. These are known as ready threads. When a processor becomes available, the system performs a context switch. The steps in a context switch are: Save the context of the thread that just finished executing.
Context Switching: Performance.Even though it’s fast, context switching is expensive: 1. Time spent is 100% overhead 2. Must invalidate other processes’ resources (caches, memory mappings) 3. Kernel must execute –it must be accessible in memory.Solution to #3:.keep kernel mapped in every process VAS.protect it to be inaccessible. File info codec.
The following classes of threads are not ready threads.
Threads created with the CREATE_SUSPENDED flag
Threads halted during execution with the SuspendThread or SwitchToThread function
Threads waiting for a synchronization object or input.
Until threads that are suspended or blocked become ready to run, the scheduler does not allocate any processor time to them, regardless of their priority.