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Memory Management Concepts
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Memory Management Concepts
Memory Management Concepts
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1
Question
What is Effective Access Time (EAT)?
Answer
EAT is a weighted average that accounts for hit ratio and relative access times of successive levels of memory.
2
Question
How is EAT calculated for two-level memory access with overlap?
Answer
EAT = H * Access_c + (1-H) * Access_MH
3
Question
What happens if access times don't overlap in the calculation of EAT?
Answer
EAT = H * Access_c + (1-H) * Access_MH + Access_c.
4
Question
What is the impact of poor locality in cache memory?
Answer
Poor locality in cache memory can cause performance degradation.
5
Question
What is a dirty block in cache memory?
Answer
A dirty block is when data is updated in the cache and the cache needs to update the memory.
6
Question
What are the two write policies for handling memory updates in cache?
Answer
1. Write-through: Slow, updates memory with each change in cache. 2. Write-back (copyback): Updates memory only when the block is about to be replaced.
7
Question
What is meant by Integrated cache and Harvard cache?
Answer
Integrated cache holds both instructions and data, while Harvard cache has separate caches for instructions and data.
8
Question
What is an advantage of Harvard cache?
Answer
Harvard cache allows for better locality but introduces more complexity.
9
Question
What is the role of a large cache?
Answer
A large cache can improve locality.
10
Question
What is the purpose of a victim cache?
Answer
A victim cache holds recently evicted blocks that can be replaced back into the cache.
11
Question
How many levels of cache are there in a system?
Answer
There are multiple levels of cache that form their own memory hierarchy.
12
Question
Where is Level 1 Cache located?
Answer
Level 1 Cache is located on the processor and has a low access time.
13
Question
Where can Level 2 Cache be found?
Answer
Level 2 Cache can be on the motherboard or an extension board.
14
Question
What is the purpose of Level 3 Cache?
Answer
Level 3 Cache sits between the processor and main memory.
15
Question
What does inclusive cache mean?
Answer
Inclusive cache means the same data can be found on different levels of cache.
16
Question
What is strictly inclusive cache?
Answer
Strictly inclusive cache guarantees that all data in a smaller cache is found in a higher level cache.
17
Question
What are exclusive caches?
Answer
Exclusive caches permit only one copy of data.
18
Question
How does virtual memory enhance performance?
Answer
Virtual memory enhances performance by providing greater memory capacity without adding main memory.
19
Question
What role does the hard disk play in virtual memory?
Answer
The hard disk is used as an extension of main memory.
20
Question
In a paging system, how is main memory organized?
Answer
Main memory is divided into page frames.
21
Question
What happens to each page in a paging system when not immediately needed?
Answer
Each page is written to disk when not immediately needed.
22
Question
What are virtual addresses?
Answer
Virtual addresses are addresses created by a program that are mapped to physical addresses.
23
Question
What is a page fault?
Answer
A page fault occurs when a program wants to access a page but can't find it in the main memory, requiring it to be fetched from virtual memory.
24
Question
What is memory fragmentation during paging?
Answer
Memory fragmentation refers to small unused clusters of memory addresses.
25
Question
What is a page table?
Answer
A page table holds all information concerning each page in disk or memory, acting as a map that links virtual pages to physical pages.
26
Question
What are the two possibilities when searching for a page in main memory?
Answer
Possibility 1: Valid bit = 1 (the page is available in memory). Possibility 2: Valid bit = 0 (the page is not in memory and needs to be retrieved from disk).
27
Question
When calculating EAT, what additional time should be accounted for in a system utilizing virtual memory?
Answer
The page table access time should be accounted for.
28
Question
What are the steps to retrieve data using a TLB?
Answer
1. CPU generates virtual address, separates it into page and offset fields. 2. Search TLB for mapping. If found, add frame to offset to make physical address and access memory. If not found, search page table in memory.
29
Question
What occurs if a page fault happens?
Answer
If there's a page fault, valid bit = 0, and the page is retrieved from disk. If memory is full, a block may need to be evicted to make space.
30
Question
What is internal fragmentation?
Answer
Internal fragmentation occurs when memory is divided into equal-sized pages, leading to unused space within allocated frames.