16. State-Aware Resource Management

Question 1

Stateful Resource Sequence

Answer 1

1. Fetch new request
2. Reconfigure resource (overhead)
3. Serve request

Question 2

Utilization of a Stateful Resource

Answer 2

• An inefficient scheduler will increase the utilization of a stateful resource

Question 3

Capacity of a Stateful Resource

Answer 3

• An efficient scheduler will increase the capacity of a stateful resource

Question 4

Example Fairness Metric for Stateful Resource

Answer 4

• The number of requests that are re-ordered before a request is served

Question 5

Seek Delay

Answer 5

• The time it takes for the disk head to align with the cylinder of the disk container the block needed to be read/written

Question 6

Rotational Delay

Answer 6

• The time it takes for the sector of the disk that contains the target block to rotate until it is under the disk head

Question 7

Transfer Time

Answer 7

• The time it takes to read/write the desired block

Question 8

Shortest Scan First (SSF)

Answer 8

• Select the request that is closest to the head position of the last processed request
• Need disk geometry and head locations

Question 9

Flaw of SSF

Answer 9

• Spatially co-located requests can delay requests for far-away block indefinitely

Question 10

SCAN

Answer 10

• Selects the next request that is closer in space to the head but only in one direction (elevator)

Question 11

Flaw of SCAN

Answer 11

• In the worst case, the head might need to travel all the way up and all the way down before servicing a request at the bottom

Question 12

C-SCAN

Answer 12

• Identical to SCAN, but limits the direction of the head to one direction only

Question 13

Complete Fair Queuing (CFQ)

Answer 13

1. Maintain one queue of requests per task, and assign a quantum of requests to be taken from each queue before moving on to the next queue, like RR
2. Re-order the requests in the dispatch queue to minimize head movement

Question 14

DRAM - Activate

Answer 14

• The entire row that is requested is copied onto a row buffer

Question 15

DRAM - Pre-Charge

Answer 15

• The row currently in the buffer is put back in place

Question 16

DRAM - First Ready, First Come First Served (FR-FCFS)

Answer 16

• A different queue is defined for each bank
• Keeps track of the row currently in the buffer
• Re-orders requests in the bank queue to prioritize row hits

Question 17

Flaw of FR-FCFS

Answer 17

• Can lead to starvation if the same row is repeatedly requested

Question 18

DRAM - Capped First Ready, First Come First Served (FR-FCFS + Cap)

Answer 18

• The same as FR-FCFS, but no more than K row-hits can be re-ordered