Operating Systems Question Bank with Answers 03

List the disadvantages of system level / kernel level threads in operating systems

Question:

List the disadvantages of system-level (kernel level) threads

Answer:

Here are the disadvantages of kernel level threads in OS;

• The kernel-level threads are slow and inefficient. For instance, threads operations are hundreds of times slower than that of user-level threads.

• Kernel threads are limited to the functionality provided by the system’s kernel. Kernel threads, though lightweight when compared to processes, are still heavily depend on kernel resources.

• Since kernel must manage and schedule threads as well as processes, it requires a full thread control block (TCB) for each thread to maintain information about threads. As a result, there is significant overhead and increased kernel complexity.

• Scheduling requires a context switch into and out of the kernel (saving registers, polluting L1/L2/L3 caches, etc.—pure overhead!)

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