Chapter 5 {{{ ------------------------------------------------------------------
2
3
5
6
7
8
    mutual exclusion
    race condition
10
    PCBS
    Allocate resources
    protect data and resources
    need mechanicsm to deal with race conditions
11
    unaware to each otehr
        basic competition
    indirectly aware
        cooperation
    directly communicating
        copoerating
12
    Mtual Exclusion
    Deadlock
    Starvation
13
    Need some way to enter critical section atomically (critical section)
14
    Data coherience == data consistent
16
    deadlock
    starvation
17
    encforcement
    non-interference
    no deadlock nor starvation
    Critical section open then something being done
    no assumptions about process speeds or cPU count
    finite time in critical section
18
    software
    hardware
    OS implementation
21
    Alternation
22
    Freed from alternation with different flags
    Problem arises when we haven't set both flags
23
    could deadlock when both set at the same time
27
    if one decides to let go at the same let go, then we have a live lock.
    neither proceeding to do instructions
29 ***
    Dekker's alogithm
    only defer if it's my turn to defer
30 ***
    Peterson's algorithm
    Simpler to code than Dekker's algorithm
32
33
    Interrupt disabling
        Option: turn off interrupts. good for 1 processor systems ONLY
34
35
    Must be performed atomically
36
37
    Pros:
        Simple and easy to verify
        permits multiple critical sections
    Cons:
        Busy waiting
        Starving
        Deadlock
38
    Semaphors
        Dijkstra in 1965
        wait(s)
        signal(s)
        Queue
39
    Strong semaphore
    Weak semaphore
        Could starve process that was repeadidly not released
40
    Semaphore different from mutex
    mutex basically a lock
    process locking is same process unlocking
41
    In general, no way to know before process calls wait whether it will block
    or not.
    What happens win process calls signal
    When you signal a semaphore
42
    Know how to go through the code
    Signal and wait are atomic functions
43
    often used for exam questions
45
47
49
51
    Expect semaphore code
    What value is going to be printed?
    What values could be printed given some number of threads running?
52
    If wait(n) and wait(s) were swapped, could possibly get deadlocked
54
    Full buffer protection
    Producer is supposed to wait for consumer(?)
    protection on empty buffer, full buffer, take, and append
57
    Barber shop
58
    Lots of stuff
60
    writer can only write at a time
    Reader effectively the same, but only first reader in and last reader out
        trigger the signal.
    Notice we can starve writer.
61
    equivalent if not more organized to semaphore
62
    monitor conceptual view
63
    conditional variable
    if no one waiting, nothing happens
64
    run through the code
65
    used for synchronization and communication (passing data)
66
    rendezvous - send and recieve both blocked
67
    definitions
68
    only 1 process can continue. all other ones are waiting. Ie only running one
    by one.
Chapter 5 }}} ------------------------------------------------------------------

Chapter 6 - Conditions of deadlock and ways to avoid {{{ -----------------------
2
    no efficient solution
    state of permanent blocking
3
    Intersection picture
4
    Deadlock code
6
    no deadlock code
8
    resuable and consume definition
14
    What are the 4 conditions of deadlock? (Very likley to be asked on the exam)
        Mutual exclusion
        hold & wait
        no preemption
        circular wait
15
    First 3 conditions give rise to the 4th
    Cannot have circular wait without the first 3
16
    Prevention
    Avoidance
    Detection
17
    Limited due to efficiency problems
    files need to be written one at a time. needs mutual exclusion
19
    Introduces delay
20
    Solution 2: setting up policy that once I can't get the next resource i
    need to get it released for others
21
    Ordering of resource requests
    not efficient
22
    Definition
23
    Methods (know definitions)
24
25 ******
    Banker's algorithm to determine saftey (most likely on the exam)
26
    Know how to do banker's algorithm
31
    know about unsafe state
32/33
    not going to be on exam probably
34
    know advantages and disadvantages
    for advantages, all but first are the big ones to be concered of
35
38
    Run through table
39
    Know the different methods for recovery
40
41
    KNow only the first 2 columns
42
    APply different strats for different groups
44
    Know the concept
46
    Dining philosipher using semaphore
47
    monitor based solution of 46
49 - END
    Skip it :D
Chapter 6 }}} ------------------------------------------------------------------

Chapter 7 - Pros/Cons of partiion schemes. Placement and buddy scheme. Pagging, address translation {{{
2
3
    Relocation
    want to protect memory from iterference of others
        mainly done by hardware
5
6
    may want memory manager to recognize pieces of program
        segmentation
7
    physically want mem manager moving one piece of memory from one place to
    another
9
    Equal-sized vs Unequal-size partition
    Internal fragmentation
13
    Using queues for fixed partition
14
    Utilization issue
16
    Know how dynamic partition works
    Problem: gaps develop ie external fragmentation
17
    compaction solve external fragmentation
    problem: takes a while
18
    Know definitions of placement alg
19
    best fit worst
    first fit tends to be best
    next-fit in the middle
25
    Know buddy system
    can mit limit on how much is wasted
    don't really have set number of things to run at once
28
    physical address actual memory addres
    logical address is what OS is using
        eg: relative addres
31
    paging and segmentation
35
    Need to keep track of everything in the page table
36
    diagram for address translation
38
    translate from logical to physical
39
    no equal sized pieces
    benefit to be able to set attributes more easily
40
    diagram for when dealing with segments
Chapter 7 }}} ------------------------------------------------------------------

Chapter 8 {{{ ------------------------------------------------------------------
2
    Characteristics
    Know last bullet
3
    Pieces in memory are resident set
4
    doing this allows more things to be loaded at once
    can run something that can't normally be ran by breaking things up
5
    virtual memory can be traded to and fro from main memory and hard drive
6
    Locality of reference allows us to do it for pages.
        Have the more widley used pages loaded for longer
8
    Must stop and load page that's not in main memory
    serious performance loss
10
    added modified bit, control bit, etc.
12
    HOw to do it with page table and virtual address
15
    Hierarchical approach
16
    Organize by frame instead of pages. Likely smaller because less frames than
    pages. Can share one table than having seperate page tables

    Search now is linear time unless doing hash lookup
21
23
    Enhanced translation conversion with TLB
24
    not indexbale
    it's associative map is in hardware
26
28
31
    show relation of page size and faulting
    If page size too large, not really getitng benefits of paging
34
    first segement number lookup
    to get page table pointer
    page table lookup to get frame number
    finally get real address
37
    paging alone or segmentatino alone is more common
40
    determine which one we want/need to override
    might rely on locality of reference
    want something simple
41
    don't want to replace locked frames
42 ****** (Important question) Clock policy most importatn
    Know how to do four page replacement algorithm
51
    lets free frame list kind of like a buffer
52-54
    Lots of stuff that I couldn't write down
57
    Understand table
58
    dealing with writing of modified pages
    demand cleaning: only write when replaced. fault handling will be longer
    though
    preclaiming: get a batch. write them out all at once. May write same thing
    over and over again repeadidly
    page buffer: best of both worlds
61
    If have too many things at once, thrashing gonna happen and performance
    drops
61
    If have too many things at once, thrashing gonna happen and performance
    drops.
62
    Know stuff
Chapter 8 }}} ------------------------------------------------------------------