rickyyx / pintos Goto Github PK

• thread_create() should set default priority
• handle (multiple/nested) donations to prevent priority inversion for locks.
• preemption on being runnable (wakeup, sleep over
• higher task wake up from block first, and sleep list
• setting of priority could trigger preemption
• ready_list to be sorted
• donations
• set priority
• get priority
• static_priority to keep track of non-donated priority

Alternative:
array of List to record priority of each thread?

• max_runnable_priority to keep track of which list to pop?
• Random access to threads with specific priority

runnable list sorted by priority?

Donations:

• On lock_acquire():
  • T donates its priority to the lock holder (if the holder is blocked?)
  • Nested donation:
    • how to find out if the lock holder is locked?

    thread needs to maintain information of the lock it is waiting for? Like, lock_waiting

• On lock_release():
  • Restores its original priority && have the highest priority thread woke up
• sema_up() needs to wake up the highest priority waiting thread.

To Do:

Minimal user program

• Argument passing
  bd39746
• User memory access
• System call infra
• exit syscall
• write syscall
• process_wait stud

wait():

1. parent exits earlier than child
2. child exits before parent calls wait() -> ZOMBIE

TODOs:

Frame Table:

Data structures:

• (hash-map<void* frame, void* page> ? Or use a struct inclusive of void* page )

• Use list of frame struct (Since no quick lookup needed)

• Obtain a frame

• Frame eviction

TODO:

• init a thread with correct recent_cpu
• init with correct load
• init thread with correct priority
• calcualte_priority

Data structure for the MLFQ

• [NUM_PRI] queues?
  -> array of lists?
  -> a rq_status 64 bits number.

For thread_tick():

• At each second:
  update_load_avg()
  update_all_recent_cpu()

• At each tick: update_cur_recent_cpu(): increment by one for current (non-idle) running thread

• At 4th tick : update_priority() (doing it first to take into account the newly created one?)

• Yield if necessary?

For thread_next_to_run():

• choose the highest queue and get the first guy.