Virtual Memory and Memory Pages Quiz
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Questions and Answers

What happens when the main memory is full in iOS?

  • The system automatically reboots.
  • No impact on the system.
  • Virtual memory is disabled.
  • Processes are terminated until there is enough free memory. (correct)

    • Why does Android not write memory pages back to flash storage on mobile devices?

  • It improves system performance significantly.
  • It drains the battery and shortens flash storage lifespan. (correct)
  • It speeds up disk access.
  • It helps in reducing virtual memory.

    • What occurs when a process needs to use memory in a memory page that triggers a page fault?

  • The memory page is mapped to a vacant memory frame. (correct)
  • The process terminates immediately.
  • The memory page is stored in flash storage.
  • The system crashes.

    • Why do virtual memory addresses differ from physical addresses?

    <p>To allow for efficient memory management and separation of processes.</p> Signup and view all the answers

    What can lead to thrashing in a system?

    <p>Running low on physical memory and constant paging.</p> Signup and view all the answers

    Why must other pages be stored on disk before loading new memory pages?

    <p>To make space in physical memory for new pages.</p> Signup and view all the answers

    What happens to the stack each time a function is called?

    <p>Grows</p> Signup and view all the answers

    Which memory area in C++ grows when memory is allocated with 'new'?

    <p>Heap</p> Signup and view all the answers

    What is the consequence of a program exceeding its maximum stack size?

    <p>Crash (stack overflow)</p> Signup and view all the answers

    In which direction does the heap generally grow in memory?

    <p>Upward</p> Signup and view all the answers

    Which memory area is shared among all threads in a running process?

    <p>Heap</p> Signup and view all the answers

    What condition is very unlikely to occur when allocating memory from the stack?

    <p>(Almost) always results in page faults</p> Signup and view all the answers

    What happens when a process accesses memory at a virtual address that is not backed by physical memory?

    <p>A page fault occurs and the memory page is loaded from disk into memory</p> Signup and view all the answers

    What is the purpose of dividing the address space into fixed-size blocks called memory pages?

    <p>To make virtual address space larger than physical address space</p> Signup and view all the answers

    What happens if a memory page needs to be evicted from main memory but has not been modified?

    <p>The page is evicted without any additional operations</p> Signup and view all the answers

    What is the consequence of having no more available page frames in main memory?

    <p>A hardware exception called a page fault takes place</p> Signup and view all the answers

    Which hardware exception occurs when a memory page is not mapped in the main memory?

    <p>Page fault</p> Signup and view all the answers

    What distinguishes iOS's handling of virtual memory from systems that support paging?

    <p>iOS does not store dirty pages on disk, only clean pages can be evicted from memory</p> Signup and view all the answers

    What is the main purpose of the custom allocator discussed in the text?

    <p>To handle all allocations using the stack instead of dynamic memory allocations</p> Signup and view all the answers

    What is the primary role of the functions allocate() and deallocate() in the custom allocator?

    <p>Forward requests to the arena for memory allocation and deallocation</p> Signup and view all the answers

    What does the rebind struct within the custom allocator template aim to do?

    <p>Change the type of elements stored in the allocator</p> Signup and view all the answers

    How are instances of ShortAlloc compared to ensure they are using the same arena?

    <p>By checking if they are pointing to the same arena</p> Signup and view all the answers

    Why is it beneficial to use an allocator and arena with a standard container?

    <p>To avoid unnecessary copies and move operations</p> Signup and view all the answers

    What is the primary state that the custom allocator holds?

    <p>Reference to the arena</p> Signup and view all the answers

    What is the main characteristic of the Mallocator struct described in the text?

    <p>Stateless allocator</p> Signup and view all the answers

    Which global functions are primarily used by the Mallocator struct for allocation and deallocation?

    <p>malloc() and free()</p> Signup and view all the answers

    What should be done when deallocating memory allocated with Mallocator?

    <p>Always deallocate with Mallocator instance</p> Signup and view all the answers

    Why is a stateless allocator considered the least complicated allocator to write?

    <p>It relies on external global state for allocation</p> Signup and view all the answers

    What makes a stateful allocator more preferable than a stateless allocator in certain scenarios?

    <p>Ability to reference specific instances</p> Signup and view all the answers

    How does the implementation of the arena class relate to the concept of stateful allocators?

    <p>Arenas benefit from stateful allocators to reference the arena instance</p> Signup and view all the answers

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