COP4600 Project 2 Minix Scheduler 2

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COP4600 Project 2Minix Scheduler 2

• Changwoo Yoon
• cwyoon_at_cise.ufl.edu

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Todays Discussion Topic

• Last Discussion Section Review
• Design of Aging Scheduler
• Project 2 Output Format
• QA

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Source Files

• cop4600.h
• Basic defines and declaration
• clock.c
• realtime should be global
• proc.h
• Add fields (priority, sub priority, utilization
  time, etc)
• proc.c
• sched(), ready(), and three functions
• system.c
• do_fork() should be modified to initialization of
  fields in struct proc

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Process Aging Algorithm

• Process Aging with Exponentially Weighted Average
• Recent past is more weighted than the distant
  past.
• IO bound v.s CPU bound processes
• P(I) CPU(I-1)/2 U(I)/2
• P(I) process priority
• CPU(I-1) exponentially weighted process util.
  Average
• U(I) process utilization

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P(I)CPU(I) CPU(I-1)/2 U(I)/2
lt- Calculated using realtime
Ticks0
40
80
80
4
30
24
I0
I1
I2
I3
CPU(0)0 U(0)0
CPU(1)U(1)/2CPU(0)/22 U(1)4 P(1)CPU(0)0
CPU(2)U(2)/2CPU(1)/216 U(2)30 P(2)CPU(1)2
CPU(3)U(3)/2CPU(2)/218 U(3)24 P(3)CPU(2)16
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How sched() is called
sched()
Clock interrupt handler
clock_handler()
do_clocktick()
Interrupt
Hardware
clock_task()
Event Message
CLOCK TASK
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realtime variable

• Use realtime variable defined in clock.c
• It keeps the system ticks
• Make it a global variable
• Use it in sched() to count the ticks between
  priority calculations
• In sched() at proc.c
• Check realtime
• Compare it with previous time
• Save current realtime as previous time
• If the difference is grater than PERIOD(40)
• Calculate priority

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U(I) - processor utilization time

• User_time Sys_time of process

Blocked or Sleep Context switch may occur
sys_time
Kernel Mode
sys_time
interrupt
restore
user_time
User Mode
user_time
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Enumerating for loop

• struct proc pr_ptr NULL
• for (pr_ptr BEG_USER_ADDR pr_ptr lt
  END_PROC_ADDR pr_ptr)
• if (!(pr_ptr-gtp_flags P_SLOT_FREE)) //
  if struc proc in use

END_PROC_ADDR
bclocked
unused
User proc
ready
unused
BEG_USER_ADDR
System/Task proc
Start of struct proc array
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So

• Use
• pr_ptr-gtuser_time
• pr_ptr-gtsys_time
• Caution this is accumulated time from the start
  of process running
• So U(I) ?
• And CPU(I) ?

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What to do in sched()?

• Priority Calculation
• At Every 2 Seconds whenever sched() is called.
  How do we count 2 seconds?
• Priority calculations for all the user processes
  (ready or blocked). How do you enumerate all
  processes? What are other type of processes?
• Scheduling
• Every 2 ticks when sched() is called
• Highest priority process first (considering both
  priority and sub priority).
• Increase sub priority by 1

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Sched()

• Check realtime
• 40 ticks past? Then calculate priority of all
  current processes
• Pick the process having lowest priority
• If the priority is same? Then compare sub
  priority
• Place THAT(picked one) at the head of rdy list.
• Increase sub priority
• Write output
• Call pick_proc() already written in sched()

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What do we need to add in process table?

• Priority
• Sub priority
• CPU(I)
• U(I)
• P(I)

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Continued

• Add appropriate variables into proc.h
• Initialization the variables at do_fork() in
  system.c

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What to do in ready()?

• Scheduling
• Ready() is called whenever a process is unblocked
  from the blocked state. Would the blocked process
  also age?
• Highest priority process first (considering both
  priority and sub priority).
• Increase sub priority by 1

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Checkup

• Which files to be included and modified?
• What should be done in clock.c?
• What should be done in system.c?
• What should be done in do_fork()?
• What should be done in proc.c?
• What should be done in sched()?
• What should be done in ready()?

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Three Output Functions

• write_string()
• writes a string passed in the argument buf to
  logfile.
• write_ready_queue()
• writes the user process ready queue to logfile
  using write_string() .
• print_ready_queue()
• prints the user process ready queue on the
  screen.

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Sample Output

• Output from sched()

Highest priority process is at the head of proc
ready list
New priority calculation starts here User proc
ready queue at 0 th sched() call within an
interval pid 40, name loop, P(i) 1, CPU(i)
0, subP(i) 1, U(i) 0, T_time 431 pid 39,
name loop, P(i) 19, CPU(i) 29, subP(i) 0,
U(i) 40, T_time 858 pid 42, name loop, P(i)
7, CPU(i) 3, subP(i) 0, U(i) 0, T_time
437 pid 43, name loop, P(i) 7, CPU(i) 3,
subP(i) 0, U(i) 0, T_time 433 pid 41,
name loop, P(i) 1, CPU(i) 0, subP(i) 0,
U(i) 0, T_time 430
U(I) CPU(I-1), CPU(I) U(I)/2 P(I)/2
Sum is about 40 ticks (2 sec.)
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Sample Output
As pid 40s subpid increased by 1, pid 41 is now
at the head of the ready queue

• New priority calculation starts here
• User proc ready queue at 0 th sched() call within
  an interval
• pid 40, name loop, P(i) 1, CPU(i) 0,
  subP(i) 1, U(i) 0, T_time 431
• pid 39, name loop, P(i) 19, CPU(i) 29,
  subP(i) 0, U(i) 40, T_time 858
• pid 42, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 437
• pid 43, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 433
• pid 41, name loop, P(i) 1, CPU(i) 0,
  subP(i) 0, U(i) 0, T_time 430
• User proc ready queue at 1 th sched() call within
  an interval
• pid 41, name loop, P(i) 1, CPU(i) 0,
  subP(i) 1, U(i) 0, T_time 430
• pid 40, name loop, P(i) 1, CPU(i) 0,
  subP(i) 1, U(i) 0, T_time 431
• pid 39, name loop, P(i) 19, CPU(i) 29,
  subP(i) 0, U(i) 40, T_time 858
• pid 42, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 437
• pid 43, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 433

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Sample Output

• User proc ready queue at 2 th sched() call within
  an interval
• pid 41, name loop, P(i) 1, CPU(i) 0,
  subP(i) 2, U(i) 0, T_time 430
• pid 40, name loop, P(i) 1, CPU(i) 0,
  subP(i) 1, U(i) 0, T_time 431
• pid 39, name loop, P(i) 19, CPU(i) 29,
  subP(i) 0, U(i) 40, T_time 858
• pid 42, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 437
• pid 43, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 433
• User proc ready queue at 3 th sched() call within
  an interval
• pid 40, name loop, P(i) 1, CPU(i) 0,
  subP(i) 2, U(i) 0, T_time 431
• pid 41, name loop, P(i) 1, CPU(i) 0,
  subP(i) 2, U(i) 0, T_time 430
• pid 39, name loop, P(i) 19, CPU(i) 29,
  subP(i) 0, U(i) 40, T_time 858
• pid 42, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 437
• pid 43, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 433

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Sample Output

• User proc ready queue at 12 th sched() call
  within an interval
• pid 40, name loop, P(i) 1, CPU(i) 0,
  subP(i) 7, U(i) 0, T_time 431
• pid 41, name loop, P(i) 1, CPU(i) 0,
  subP(i) 6, U(i) 0, T_time 430
• pid 39, name loop, P(i) 19, CPU(i) 29,
  subP(i) 0, U(i) 40, T_time 858
• pid 42, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 437
• pid 43, name loop, P(i) 7, CPU(i) 3,
  subP(i) 0, U(i) 0, T_time 433
• New priority calculation starts here
• User proc ready queue at 0 th sched() call within
  an interval
• pid 40, name loop, P(i) 0, CPU(i) 11,
  subP(i) 1, U(i) 22, T_time 453
• pid 41, name loop, P(i) 0, CPU(i) 9,
  subP(i) 0, U(i) 18, T_time 448
• pid 39, name loop, P(i) 29, CPU(i) 14,
  subP(i) 0, U(i) 0, T_time 858
• pid 42, name loop, P(i) 3, CPU(i) 1,
  subP(i) 0, U(i) 0, T_time 437
• pid 43, name loop, P(i) 3, CPU(i) 1,
  subP(i) 0, U(i) 0, T_time 433

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Sample Output

• Output from ready()

User proc ready queue at -1 th sched() call
within an interval pid 44, name doze, P(i)
0, CPU(i) 0, subP(i) 0, U(i) 0, T_time
0 pid 42, name loop, P(i) 0, CPU(i) 6,
subP(i) 1, U(i) 12, T_time 28 pid 39, name
loop, P(i) 20, CPU(i) 15, subP(i) 0, U(i)
10, T_time 60 pid 41, name loop, P(i) 0,
CPU(i) 5, subP(i) 0, U(i) 10, T_time
26 pid 43, name loop, P(i) 0, CPU(i) 5,
subP(i) 0, U(i) 10, T_time 28 pid 40, name
loop, P(i) 15, CPU(i) 7, subP(i) 0, U(i)
0, T_time 86
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Output printing

• Maintain tick_counter in sched()
• Call write_ready_queue(tick_counter) before
  pick_proc()
• In ready()
• Call write_ready_queue(-1) before end of
  function

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Project 2 Q A

• Any questions?

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