EDF POLLING SERVER

Harish Chetty

Lots of Problems!• Had to read about 20,000 Lines of Code Spread across 7 unrelated files.

• Had to read through 2000 more lines to interpret Mark’s Sporadic server!

• Understood about 20% code (which I thought was 80% at the beginning).

• Reinstalled Kernel about 500 Times.

• Found out limitations of printk’s!

• Some crash caused Disk(or something to corrupt) forcing use of TTY.

• SMP’s made life hell.

• CBS ensured PS to always fail!

• Finally the last phase was carried out on kernel which took 20 minutes to compile.

• HAD TO FINALLY UNDERSTAND ABOUT 50% TO GET STUFF DONE!

IMAGINE A CLOCK!

Rings Bell Every 60 Seconds Period : 60 sec Must Ring Bell for 5 Seconds Budget: 5 sec Complete Ringing in 10 Second Deadline: 10 sec

Submit Task

Setup Deadline& Budget

EnqueueTask

DequeueTask

Budget Exhausted

Budget Left

When the task must end!

How much time the task should run?

?TaskDead

TASK COMPLETE/KILL

KILL

Wakeup task,Run the task,

Update Runqueues etc.

Schedule task,Block the task,

Push task in wating queue etc.

Submit Task

Setup Deadline (D),

Budget (B)& Replenishment

Timer (RT)

EnqueueTask

DequeueTask

B = Cap

RT TimeoutB = 0

?

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Release Replenishment Timer

(RT)

Submit Task

Setup(D), (B)& (RT)

EnqueueTask

DequeueTask

B = (RQ TIME – START TIME)

RT TimeoutB = 0

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Task Running

UpdateStatus

B = Cap

B = Cap

B = 0

CPU RUNQUEUE TIME

INITIAL BUDGET

Release (RT)

Submit Task

Setup(D), (B)& (RT)

EnqueueTask

DequeueTask

B = (RQ TIME – START TIME)

RT TimeoutB = 0

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Task Running

UpdateStatus

B = 0 / B = Cap

B = Cap

B = 0

Release (RT)

Submit Task

Setup(D), (B)& (RT)

EnqueueTask

DequeueTask

B = (RQ TIME – START TIME)

RT TimeoutB = 0

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Task Running

UpdateStatus

B = 0 / B >= Cap

B = Cap

B = (0 + P)

OVERRUN TIME (Penalty (P))

Release (RT)

WHAT IF MORE THAN ONE TASK?

WHAT IF MORE THAN ONE TYPE OF TASK?

SCHED_OTHER (CFS) SCHED_RT SCHED_DEADLINE

BATCH IDLE

NORMAL EDF FIFOROUND ROBIN

IDLE TASK SCHED_POLL

99 to 0132 to 100> 132 -1 -2

Submit Task

Setup(D), (B)& (RT)

EnqueueTask

P = -2

DequeueTask

B = (RQ TIME – START TIME)

RT TimeoutB = 0

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Task Running

UpdateStatus

B = 0 / B >= Cap

B = Cap

B = (0 + P)

Release (RT)

Submit Task

Setup(D), (B)& (RT)

EnqueueTask

P = -2

DequeueTask

B = (RQ TIME – START TIME)

RT TimeoutB = 0

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Task Running

UpdateStatus

B = 0 / B >= Cap

B = Cap

B = (0 + P)

Release (RT)

Forward

RQ TIME == Deadline!

D = D + D

Why NOT 2D ?? Here comes Periods!

WHAT IF MORE THAN ONE CPU?

Submit Task

Setup(D), (B)& (RT)

EnqueueTask

P = -2

DequeueTask

B = (RQ TIME – START TIME)

RT TimeoutB = 0

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Task Running

UpdateStatus

B = 0 / B >= Cap

B = Cap

B = (0 + P)

Release (RT)

Forward

RQ TIME == Deadline!

D = D + D

SMP Enqueue

TaskP = -2

SMPDequeue

Task

RT TimeoutB = 0B = (0 + P)

N(CPU) > 1

Submit Task

Setup(D), (B)& (RT)

EnqueueTask

P = -2

DequeueTask

B = (RQ TIME – START TIME)

RT TimeoutB = 0

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Task Running

UpdateStatus

B = 0 / B >= Cap

B = Cap

B = (0 + P)

Release (RT)

Forward

RQ TIME == Deadline!

D = D + D

SMP Enqueue

TaskP = -2

SMPDequeue

Task

RT TimeoutB = 0

B = (0 + P)

N(CPU) > 1

SelectCPU

WHAT IF MORE THAN ONE SCHED_POLL TASK?

Submit Task

Setup(D), (B)& (RT)

EnqueueTask

P = -2

DequeueTask

B = (RQ TIME – START TIME)

RT TimeoutB = 0

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Task Running

UpdateStatus

B = 0 / B >= Cap

B = Cap

B = (0 + P)Release (RT)

Forward

RQ TIME == Deadline!

D = D + D

SMP Enqueue

TaskP = -2

SMPDequeue

Task

RT TimeoutB = 0

B = (0 + P)

N(CPU) > 1

SelectCPU

Pick Next Task

Preemptverifier

volatile long long int count =0;while(1){ if(count<1000000){

count++;printf("Printing number %lld \n", count);

} else{

break; }}

I WILL STOP BORING YOU AND END!

EXTRAS

Data Structures• Pick Next Tasks use RB Trees based on Deadlines.

• Leftmost Node is cached (smallest Deadline)

• CPU’s work using Max Heaps based on task deadlines.• Root Node has CPU with a task with the largest Deadline. Preempt this first

if necessary• Must be a Queue for more efficiency??

• Waiting Tasks use RB Trees based on Deadlines.• Leftmost Node is cached (smallest Deadline)

Submit Task

Setup Deadline& Budget

EnqueueTask

DequeueTask

Budget Left = 0

Budget Left != 0

When the task must end!

How much time the task should run?

?

Wakeup task,Run the task,

Update Runqueues etc.

Schedule task,Block the task,

Push task in wating queue etc.

Submit Task

Setup(D), (B)& (RT)

EnqueueTask

P = -2

DequeueTask

B = (RQ TIME – START TIME)

RT TimeoutB = 0

TaskDead

TASK COMPLETE/KILL

KILL

INIT Task

Task Running

UpdateStatus

B = 0 / B >= Cap

B = Cap

B = (0 + P)Release (RT)

Forward

RQ TIME == Deadline!

D = D + D

SMP Enqueue

TaskP = -2

SMPDequeue

Task

RT TimeoutB = 0

B = (0 + P)

N(CPU) > 1

SelectCPU

Pick Next Task