Question about Operating Systems A computer has 4 GB of RAM of which the operati

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Question about Operating Systems

A computer has 4 GB of RAM of which the operating system occupies 512 MB. The processes are all 256 MB (for simplicity) and have the same characteristics. If the goal is 99% CPU utilization, what is the maximum I/O wait that can be tolerated? Use the simple multiprogramming model we presented in the slides to solve this problem. You can assume that the impact of context switches is negligible. List one advantage each for implementing threads in user space and in kernel space. For each implementation, also list a disadvantage.

Explanation / Answer

8). All processes is required to fit in memory, suppose there are N process then altogether the os will take 512+256 N. MB. As there is single room for 4096 MB. It is needed 512+256 N <= 4096. Dividing both side by 256 this will give 2+ N <=16.

9)User space thread implementation:

Advantage- the user space thread package could be implemented on an os which do not support thread. All os is needed to fall into this category.

Disadvantage- there is a problem on blocking system call

Kernel space thread--

Advantage- the thread operation can be implemented in the is and kernel scheduler.

Disadvantage- the kernel space thread are fund to be slow and in efficient.

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