Describe the use of a directed graph defined by a set of vertices V (each vertex

Question

Describe the use of a directed graph defined by a set of vertices V (each vertex belonging exclusively to either a set of active processes P or to a set of all resources R), and a set of edges E (each edge representing either a process requesting a resource expressed as Pi Right arrow Ri or a resource assigned to a process Rj Right arrow Pj) to determine if a deadlock occurs in a system. Design a multi-level scheduler that expects a variety of process needs. Justify your solution. Briefly describe the boot process of an PC operating system shown in the following diagram: Given a CPU with hardware support for a paging table using a valid/invalid bit for each page, a physical memory size, an addressing size, and GB file system size, design a Virtual Memory/Page Replacement System to take best advantage of the hardware. Justify your solution. Describe the problems created by using a memory system that may result in page faults on CPU scheduling. Compare and contrast the Best Fit and First Fit Memory Management with the paging solution. Explain the principle of Critical Sections. Use the Java Synchronization mechanism to demonstrate the design of processes that have critical sections.

Explanation / Answer

5.The hardware that detects a page fault is the processor's memory management unit(MMU), while the exception handlingsoftware that handles page faults is generally a part of the operating system kernel.

F

Accessing a page that isn’t resident in memory but is on disk in a page file or a mapped file - Allocate a physical page, and read the desired page from disk and into the relevant working set

Accessing a page that is on the standby or modified list - Transition the page to the relevant process, session, or system working set

Accessing a demand-zero page - Add a zero-filled page to the relevant working set

Writing to a copy-on-write page - Make process-private (or session-private) copy of page, and replace original in process or system working set

Best Fit:The allocator places a process in the smallest block of unallocated memory in which it will fit. For example, suppose a process requests 12KB of memory and the memory manager currently has a list of unallocated blocks of 6KB, 14KB, 19KB, 11KB, and 13KB blocks. The best-fit strategy will allocate 12KB of the 13KB block to the process.

Worst fit: The memory manager places a process in the largest block of unallocated memory available. The idea is that this placement will create the largest hold after the allocations, thus increasing the possibility that, compared to best fit, another process can use the remaining space. Using the same example as above, worst fit will allocate 12KB of the 19KB block to the process, leaving a 7KB block for future use.

3.

er for a computer to successfully boot, its BIOS, operating system and hardware components must all be working properly; failure of any one of these three elements will likely result in a failed boot sequence.

When the computer's power is first turned on, the CPUinitializes itself, which is triggered by a series of clock ticks generated by the system clock. Part of the CPU's initialization is to look to the system's ROM BIOS for its first instruction in the startup program. The ROM BIOS stores the first instruction, which is the instruction to run the power-on self test (POST), in a predetermined memory address. POST begins by checking the BIOS chip and then tests CMOS RAM. If the POST does not detect a battery failure, it then continues to initialize the CPU, checking the inventoried hardware devices (such as the video card), secondary storage devices, such as hard drives and floppy drives, ports and other hardware devices, such as the keyboard and mouse, to ensure they are functioning properly.

Once the POST has determined that all components are functioning properly and the CPU has successfully initialized, the BIOS looks for an OS to load.

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