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Lecture 7 Disc Scheduling. Lecture Highlights Introduction to Disc Management Need for disc scheduling Disc Structure Details of disc speed

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  • Lecture 7Disc Scheduling

  • Lecture HighlightsIntroduction to Disc ManagementNeed for disc schedulingDisc StructureDetails of disc speedDisc Scheduling AlgorithmsParameters InvolvedParameter-Performance RelationshipsSome Sample Results

  • Introduction to Disc ManagementDisk systems are the major secondary-storage I/O device on most computers. One of the functions of the memory manager is to manage swapping between main memory and disk when main memory is not big enough to hold all the processes. The disk, i.e. the secondary storage device, at the same time needs effective management in terms of disc structure and capacity, the disc writing mechanism and the scheduling algorithm choice.

  • Introduction to Disc ManagementNeed for disc scheduling Requests for disk I/O are generated both by the file system and by virtual-memory systems.Since most jobs depend heavily on the disc for program loading and input and output files, it is important that disk service be as fast as possible.The operating system can improve on the average disk service time by scheduling the requests for disc access.

  • Introduction to Disc ManagementDisc StructureA disc can be viewed as a set of platters on top of each other.Each platter has two surfaces.Each surface is divided into tracks which are concentric.Each track is further divided into a number of sectors.A sector is the smallest unit of information that can be read from or written to the disc. In other words, a sector is the smallest addressable portion of the disc.Hard Disc Structure:

    plattersread-write headsspindletrackssectors

  • Introduction to Disc ManagementDisc StructureTo access a sector surface, track and sector need to be specified i.e. information on the disc is referenced by a multipart address, which includes the drive number, the surface, the track, and the sector. All the tracks on one drive that can be accessed without the heads being moved (the equivalent tracks on the different surfaces) constitute a cylinder.Each track has equal capacity which means that inner tracks are more densely coated. This allows the read-write head to have the same velocity over each track.

  • Introduction to Disc ManagementDisc StructureSectors vary from 32 bytes to 4096 bytes; usually, they are 512 bytes in size.There are 20 to 1500 tracks per disc surface. I/O transfers between memory and disc are performed in units of one or more sectors, called blocks, to improve I/O efficiency.

  • Introduction to Disc ManagementDetails of disc speedThe disk movement is composed of three parts. The three distinct physical operations, each with its own cost, are: seek timerotational delay/latency timetransfer time. After looking into the three operations in some more details, specifications of three disc drives from past and present are included to give you a realistic idea of the concerned parameters and how the technology has been advancing.

  • Details of disc speedSeek TimeTo access a block on the disk the system must first move the head to the appropriate track or cylinder. This head movement is called a seek, and the time to complete it is seek time.The amount of time spent seeking during a disc access depends on how far the arm has to move (more explanation follows on the next slide).

  • Details of disc speedSeek TimeIf we are accessing a file sequentially and the file is packed into several consecutive cylinders, seeking needs to be done only after all the tracks on a cylinder have been processed, and then the read/write head needs to move the width of only one track (minimum seek time/ track-to-track seek time). At the other extreme, if we are alternately accessing sectors from two files that are stored at opposite extremes on a disk, seeking is very expensive (could be full stroke/ max seek time).Consequently, if we were to write to an empty disc, it is more efficient to do the writing cylinder wise as it reduces seek time.

  • Details of disc speedSeek TimeSeeking is likely to be more costly in a multi-user environment, where several processes are contending for use of the disk at one time, than in a single-user environment, where disk usage is dedicated to one process. This is so because in a multi-user environment the different users might be seeking files at different locations.Since seeking can be very costly, system designers often go to great extremes to minimize seeking. In an application that merges three files, for example, it is not unusual to see the three input files stored on three different drives and the output file stored on a fourth drive, so no seeking need be done as I/O operations jump from file to file.

  • Details of disc speedSeek TimeSince it is usually impossible to know exactly how many tracks will be traversed in a seek, we usually try to determine the average seek time required for a particular operation. If the starting and ending positions for each access is random, it turns out that the average seek traverses one-third of the total number of cylinders that the read/write head ranges over.Most hard discs available today have average seek times of less than 10ms and high performance discs have average seek times as low as 7.5ms.

  • Details of disc speedLatency Time / Rotational DelayOnce the head is at the right track, it must wait until the desired block rotates under the read-write head. This delay is the latency time.Hard discs usually rotate at about 5000 rpm, which is one revolution per 12ms. On average, the rotational delay is half a revolution, or about 6ms. As in the case of seeking, these averages apply only when the read/write head moves from some random place on the disc surface to the target track. In many circumstances, rotational delay can be much less than the average.

  • Details of disc speedTransfer Time Once the data we want is under the read/write head, it can be transferred . The transfer time is given by the formula:Transfer time = number of bytes transferred X rotation time number of bytes on a trackIf a disc is sectored, the transfer time for one sector depends on the number of sectors on a track. For example, if there are 63 sectors per track, the time required to transfer one sector would be 1/63 of a revolution.

  • Details of disc speedSample specifications of discs (from past)

    CharacteristicSeagate Cheetah 9Western Digital Caviar AC22100Western Digital Caviar AC2850Capacity 9000MB2100MB850MBMin. seek time0.78ms1ms1msAv. Seek time8ms12ms10msMax. seek time19ms22ms22msSpindle speed10000rpm5200rpm4500rpmAv rotational delay3ms6ms6.6msMax. transfer rate14506 bytes/ms2796 bytes/ms2419 bytes/msBytes per sector512512512Sectors per track1706363Tracks per cylinder161616Cylinders52640921654

  • Details of disc speedSample specifications of discs (at present)

    CharacteristicIBM Deskstar 120GPWestern Digital Caviar 1200BBCapacity 120GB120GBMin. seek time1.2ms2msAv. Seek time8.5ms8.9ms(read seek) 10.9ms(write seek)Max. seek time14.7ms21msSpindle speed7200rpm7200rpmAv rotational delay4.17ms4.2msBuffer to disc transfer rate592Mbits/s602Mbits/sBytes per sector512512Sectors per trackNot specified63Tracks per cylinderNot specifiedNot specifiedCylindersNot specified16,383

  • Introduction to Disc ManagementSummary of disc speedThe total time to service a disk request is the sum of the seek time, latency time, and transfer time. For most disks the seek time dominates, so reducing the mean seek time can improve the system performance substantially. Thus, the primary concern of disc scheduling algorithms is to minimize seek and latency times.

  • Disc Scheduling AlgorithmsFirst Come First Serve (FCFS)FCFS is the simplest form of disc schedulingThis algorithm is easy to program and is intrinsically fair.However, it may not provide the best service.The example on the next page illustrates FCFS scheduling.

  • Disc Scheduling AlgorithmsFirst Come First Serve (FCFS)Suppose an ordered disc queue with requests involving tracks98, 183, 37, 122, 14, 124, 65, 67If the read-write head is initially at track 53, it will first move to 98, then to 183, 37, 122, 14, 124, 65 and finally to 67 (as depicted by the figure on the next slide).In this case, total head movement = 640 tracks.

  • Disc Scheduling AlgorithmsFirst Come First Serve (FCFS)

  • Disc Scheduling AlgorithmsShortest Seek Time First (SSTF)The SSTF algorithm selects the request with the minimum seek time from the current head position.Since seek time is generally proportional to the track difference between the requests, this approach is implemented by moving the head to the closest track in the request queue.Well use the same sequence of requests as used in the FIFO example to illustrate SSTF scheduling.

  • Disc Scheduling AlgorithmsShortest Seek Time First (SSTF)Suppose an ordered disc queue with requests involving tracks98, 183, 37, 122, 14, 124, 65, 67If the read-write head is initially at track 53, it will first move to 65, then to 67, 37, 14, 98, 122, 124, and finally to 183 (as depicted by the figure on the next slide).In this case, total head movement = 236 tracks.SSTF results in a substantial improvement in average disk service but suffers from the potential of starvation (specially in case of dynamic requests).

  • Disc Scheduling AlgorithmsShortest Seek Time First (SSTF)

  • Disc Scheduling AlgorithmsSCAN SchedulingThe read-write head starts at one end of the disc, and moves toward the other end, servicing requests as it reaches each track, until it gets to the other end of the disc. At the other end, the direction of head movement is reversed and servicing continues.The head continuously scans the disc from end to end.SCAN algorithm is also called the elevator algorithm.Lets apply this algorithm to the same example.

  • Disc Scheduling AlgorithmsSCAN SchedulingWell use the same request sequence98, 183, 37, 122, 14, 124, 65, 67If the read-write head is initially at track 53 moving towards 0, it will first service 37 and 14, change directions and service 65, 67, 98, 122, 124, and finally 183 (as depicted by the figure on the next slide). Moreover, if a request arrives in the queue just in front of the head, it will be serviced almost immediately.However, if a request arrives in the queue just behind the head it will have to wait for almost two full cycles.

  • Disc Scheduling AlgorithmsSCAN Scheduling

  • Disc Scheduling AlgorithmsC-SCAN SchedulingA variant of SCAN scheduling that is designed to provide a more uniform wait time is C-SCAN (circular SCAN) scheduling.As does SCAN scheduling C-SCAN scheduling moves the head from one end of the disc to the other, servicing requests as it goes.When it reaches the other end, however, it immediately returns to the beginning of the disc, without servicing any requests on the return trip.The C-SCAN algorithm essentially treats the disc as though it were circular, with the last track adjacent to the first one.

  • Disc Scheduling AlgorithmsC-SCAN SchedulingLets take a look at the processing of our request queue: 98, 183, 37, 122, 14, 124, 65, 67 in this case.The order of processing starting at 53 would be 65, 67, 98, 122, 124, 183, 14 and 37 (as depicted by the figure on the next slide).

  • Disc Scheduling AlgorithmsC-SCAN Scheduling

  • Disc Scheduling AlgorithmsLOOK and C-LOOK SchedulingBoth SCAN and C-SCAN scheduling always move the head from one end of the disk to the other.In practice, neither algorithm is implemented in this way. More commonly, the head is only moved as far as the last request in each direction. As soon as there are no requests in the current direction, the head movement is reversed.These versions of SCAN and C-SCAN scheduling are called LOOK and C-LOOK scheduling (see figure on next slide).

  • Disc Scheduling AlgorithmsC-LOOK Scheduling

  • Disc Scheduling AlgorithmsSelecting a disc scheduling algorithmWith any scheduling algorithm, performance depends heavily on the number and types of requests.If the queue seldom has more than one outstanding request, then all scheduling algorithms are effectively equivalent and FIFO would be a reasonable choice.The SCAN and C-SCAN algorithms are more appropriate for systems that place a heavy load on the disc.

  • Parameter InvolvedDisc access time (seek time, latency time and transfer time)Disc configuration Disc scheduling algorithm Disc writing mechanism (where to rewrite processes after processing them in RAM)Disc capacity

  • Parameter InvolvedEffect of Disc Access Time The lower is the value of this parameter, the better is the system performance. As explained earlier in the lecture, seek time, latency time and transfer time together give the disc access time. Since seek is the most expensive of the three operations, lowering seek time is crucial to system efficiency.

  • Parameter InvolvedEffect of Disc Configuration Disk configuration relates to the structural organization of the disc into tracks and sectors. Disc surfaces and tracks are determined by hardware specifications. However, some operating systems allow the user to choose the sector size that influences the number of sectors per track. It is an entire sector that is read or written when transfer occurs. The number of tracks equals the number of cylinders. Reading and writing on one cylinder reduces the seek time considerably. This property determines efficiency of many computing algorithms and determines inter-record and intra-record fragmentation in terms of database operationsIt also affects system performance in operations like disc defragmentation ( a rewriting mechanism).

  • Parameter InvolvedEffect of Disc Scheduling Algorithm This is the parameter that primarily determines the possible minimization of seek and latency times. While FCFS algorithm is easy to program and is intrinsically fair, however, it may not provide the best service. SSTF scheduling substantially improves the average service time but suffers from the inherent problem of starvation of certain processes in case of continuing/dynamic flow of requests.

  • Parameter InvolvedEffect of Disc Scheduling AlgorithmThe SCAN, C-SCAN, LOOK and C-LOOK belong to the more efficient genre of disk scheduling algorithms. These are however, complicated in their respective implementations and are more appropriate for systems that place a heavy load on the disk. With any scheduling algorithm, however, performance depends heavily on the number and types of requests. In particular, if the queue seldom has more than one outstanding request, then all scheduling algorithms are effectively equivalent. In this case, FCFS scheduling is also a reasonable algorithm.

  • Parameter InvolvedEffect of Disk Writing Mechanism In terms of disk writing mechanism, there is a choice between writing back to where the process was initially read from and writing back to the closest cylinder to the disk head where there is an empty sector. While the former is straightforward to implement in no way does it attempt an optimization of seek time. The latter choice, however, results in increased overhead in terms of updating the location of the process every time it is written back to the disk.

  • Performance MeasuresAverage Waiting TimeAverage Turnaround TimeCPU utilizationCPU throughputPercentage seek timeThis is a new performance measure and it quantifies latency costCalculated as a percentage of total timePercentage latency timeThis is a new performance measure and it quantifies latency costCalculated as a percentage of total time

  • Disc SchedulingImplementationAs part of Assignment 5, youll implement a memory manager system including a Disc simulator within an operating system satisfying the given requirements. (For complete details refer to Assignment 5)Well see a brief explanation of the assignment in the following slides.

  • Disc SchedulingImplementation DetailsFollowing are some specifications of the system youll implement:Youll use the memory and job mix description in Assignment 3Disc access time = Seek + Latency + (job size(in bytes) / 500000) ms (Transfer time)( youll recall that in Assignment 3 we had used a constant value of 1ms instead of seek and latency times but here the same shall be a variable and you could study the effect of it on system performance)Disc has eight surfaces, 300 tracks/surfaceUse your own latency and seek time rates (should be a program variable)Make the Disc Scheduling mechanism a variable (SSTF/ FIFO / ..etc.)

  • Disc SchedulingImplementation DetailsAfter completing the implementation and doing a few sample runs, start thinking of this problem from an algorithmic design point of view. The algorithm/hardware implementation of the memory manager/Disc manager involves many parameters, some of them include:Memory SizeDisc access time (transfer time, latency and seek)Time slot for RRCompaction thresholds (percentage and hole size)RAM access time(Continued on the next slide)

  • Disc SchedulingImplementation Details Some of the involved parameters (continued from the last slide):Fitting algorithmDisc Scheduling algorithm choice (FIFO, SSTF, SCAN, LOOK, etc.)Disc structure and capacity (surfaces, tracks, etc.)Disc writing mechanism (where to write back processed pages)

  • Disc SchedulingImplementation DetailsThe eventual goal would be to optimize several (or some) performance measures (criteria) such as:Average waiting timeAverage turnaround timeMaximum waiting timeMaximum turnaround timeCPU utilizationCPU throughputMemory fragmentation over timeDisc fragmentation over time

  • Disc SchedulingImplementation Details After you are done with the assignment, you have the opportunity to attempt the following two bonus questions:Bonus Question 1: Implement the above using a paging mechanism (1-level) (I.e. divide each jobs to a number of pages, given a fixed page size). Implement a page replacement algorithm (or more) to decide which pages to replace and to anticipate page usage throughout the simulation. You have to implement a randomizer to simulate page access patterns for different processes. Try different dynamic algorithms for deciding on the number of memory pages to be assigned to a process through the life of a process in the system (dynamically).

  • Disc SchedulingImplementation DetailsBonus Question 2: Study and analyze the behavior of the combined memory system and Disc (the performance measures) based on parameter changes as above and incorporate the following parameters:Page SizePage replacement and paging anticipation algorithm choiceDisc writing algorithm choice (how and where to write jobs back to disc)

  • Disc SchedulingSample Screenshots of SimulationSetting variable parameters

  • Disc SchedulingSample Screenshots of SimulationSetting variable parameters (contd.)

  • Disc SchedulingSample Screenshots of SimulationInitial Hard Disc Configuration

  • Disc SchedulingSample Screenshots of SimulationInitial RAM Configuration

  • Disc SchedulingSample Screenshots of SimulationMemory manage with disc scheduler in execution

  • Disc SchedulingSample Screenshots of SimulationFinal Performance Measures for the run

  • Disc SchedulingSample tabulated data from simulationAlgorithm combinations vs. Performance MeasuresFixed Parameters:RR Time Slot: 2msAverage Seek Time: 8msSimulation Time: 3000msSector Size: 1KBAverage Latency Time: 4ms

  • Disc SchedulingCorresponding graph for table on previous slide

    Chart32

    99829982

    7.9416.7814.8518.62

    10779441068943

    10739401064939

    55.0811.0715.991.32

    21.4831.2140.1734.64

    SERIES INDEXSeries1 FIFO, First Fit Series2 FIFO, Best FitSeries3 SSTF, First FitSeries4 SSTF, Best Fit

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Algorithm Combinations

    Algorithm Combination vs. Performance Measures

    Sheet1

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2997.941077107355.0821.48

    416813.6671971650.8920.13

    620017.3227727447.7719.77

    824720.5126325945.9019.14

    Sheet1

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performances Measures

    RR Time Slot

    RRTimeSlot vs. Performance Measures using FIFO- First Fit algorithm combination

    Sheet2

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    49910.961071106838.0029.64

    6999.211074107047.9024.91

    8997.941077107355.0821.48

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    Sheet2

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet3

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2998.901075107161.7012.03

    4997.941077107355.0821.48

    6997.171079107549.7329.10

    8996.541081107745.3435.36

    Sheet3

    SERIES INDEXSeries1 AvLatencytime: 2Series2 AvLatencytime :4Series3 AvLatencytime: 6Series4 AvLatencytime: 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet4

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28216.7894494011.0731.21

    411321.7778077612.5026.47

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    Sheet4

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet5

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    48217.769439405.8633.04

    68217.259439408.5432.10

    88216.7894494011.0731.21

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    Sheet5

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet6

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28219.8894193813.1218.49

    48216.7894494011.0731.21

    68214.519469429.5840.50

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    Sheet6

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    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using FIFO-Best Fit algorithm combination

    Sheet7

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29914.851068106415.9940.17

    416823.4371471015.7334.55

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    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing SSTF-First Fit algorithm combination

    Sheet8

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    49916.14106710648.6943.66

    69915.471068106412.4941.84

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    Sheet8

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet9

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29918.581066106220.0125.13

    49914.851068106415.9940.17

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    Sheet9

    SERIES INDEXSeries1 AvLatencytime: 2Series2 AvLatencytime :4Series3 AvLatencytime: 6Series4 AvLatencytime: 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet10

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

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    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTime Slot vs. Performance Measures using SSTF-Best Fit algorithm combination

    Sheet11

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    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing SSTF-Best Fit algorithm combination

    Sheet12

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

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    Sheet12

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    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using SSTF-Best Fit algorithm combination

    Sheet13

    Sector Size (KB)Throughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    19914.851068106415.9940.17

    29914.851068106415.9940.17

    49914.851068106415.9940.17

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    Sheet13

    SERIES INDEXSeries1 SectorSize: 1Series2 SectorSize: 2Series3 SectorSize: 4Series4 SectorSize: 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Sector Size

    Sector Size vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet14

    Algorithm CombinationThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency Time

    FIFO, First Fit997.941077107355.0821.48

    FIFO, Best Fit8216.7894494011.0731.21

    SSTF, First Fit9914.851068106415.9940.17

    SSTF, Best Fit8218.629439391.3234.64

    Sheet14

    SERIES INDEXSeries1 FIFO, First Fit Series2 FIFO, Best FitSeries3 SSTF, First FitSeries4 SSTF, Best Fit

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Algorithm Combinations

    Algorithm Combination vs. Performance Measures

  • Disc SchedulingSample tabulated data from simulationAverage Seek Time vs. Performance Measures (using FIFO-first fit algorithm combination)Fixed Parameters:RR Time Slot: 2msSimulation Time: 3000msSector Size: 1KBAverage Latency Time: 4ms

  • Disc SchedulingCorresponding graph for table on previous slide

    Chart25

    99999999

    10.969.217.946.98

    1071107410771080

    1068107010731076

    3847.955.0860.51

    29.6424.9121.4818.88

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet1

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2997.941077107355.0821.48

    416813.6671971650.8920.13

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    824720.5126325945.9019.14

    Sheet1

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performances Measures

    RR Time Slot

    RRTimeSlot vs. Performance Measures using FIFO- First Fit algorithm combination

    Sheet2

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    49910.961071106838.0029.64

    6999.211074107047.9024.91

    8997.941077107355.0821.48

    10996.981080107660.5118.88

    Sheet2

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet3

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2998.901075107161.7012.03

    4997.941077107355.0821.48

    6997.171079107549.7329.10

    8996.541081107745.3435.36

    Sheet3

    SERIES INDEXSeries1 AvLatencytime: 4Series2 AvLatencytime :6Series3 AvLatencytime: 8Series4AvLatencytime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet4

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28216.7894494011.0731.21

    411321.7778077612.5026.47

    612422.8358157611.7424.50

    813723.50454011.0723.29

    Sheet4

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet5

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    48217.769439405.8633.04

    68217.259439408.5432.10

    88216.7894494011.0731.21

    108216.3294494013.4730.37

    Sheet5

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet6

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28219.8894193813.1218.49

    48216.7894494011.0731.21

    68214.519469429.5840.50

    88212.799489448.4447.57

    Sheet7

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29914.851068106415.9940.17

    416823.4371471015.7334.55

    620028.3927226914.3932.41

    824734.642582548.6532.31

    Sheet7

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing SSTF-First Fit algorithm combination

    Sheet8

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    49916.14106710648.6943.66

    69915.471068106412.4941.84

    89914.851068106415.9940.17

    109914.281069106519.2238.62

    Sheet8

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet9

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29918.581066106220.0125.13

    49914.851068106415.9940.17

    69912.361070106613.3150.18

    89910.591073106911.4157.31

    Sheet10

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    28218.629439391.3234.64

    411324.447807761.7629.72

    612425.495805751.4227.37

    813726.1045401.2225.86

    Sheet10

    SERIES INDEXSeries1 RRSlot = 2Series2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTime Slot vs. Performance Measures using SSTF-Best Fit algorithm combination

    Sheet11

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    48218.749439390.6634.87

    68218.789439390.9934.75

    88218.629439391.3234.64

    108218.559439401.6434.52

    Sheet11

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing SSTF-Best Fit algorithm combination

    Sheet12

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    28222.529419371.5920.94

    48218.629439391.3234.64

    68215.879459421.1244.28

    88213.839489440.9851.45

    Sheet13

    Sector Size (KB)Throughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    19914.851068106415.9940.17

    29914.851068106415.9940.17

    49914.851068106415.9940.17

    89915.231068106416.4438.58

    Sheet14

    Algorithm CombinationThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency Time

    FIFO, First Fit997.941077107355.0821.48

    FIFO, Best Fit8216.7894494011.0731.21

    SSTF, First Fit9914.851068106415.9940.17

    SSTF, Best Fit8218.629439391.3234.64

  • Disc SchedulingSample tabulated data from simulationAverage Seek Time vs. Performance Measures (using SSTF-first fit algorithm combination)Fixed Parameters:RR Time Slot: 2msSimulation Time: 3000msSector Size: 1KBAverage Latency Time: 4ms

  • Disc SchedulingCorresponding graph for table on previous slide

    Chart26

    99999999

    16.1415.4714.8514.28

    1067106810681069

    1064106410641065

    8.6912.4915.9919.22

    43.6641.8440.1738.62

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet1

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2997.941077107355.0821.48

    416813.6671971650.8920.13

    620017.3227727447.7719.77

    824720.5126325945.9019.14

    Sheet1

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performances Measures

    RR Time Slot

    RRTimeSlot vs. Performance Measures using FIFO- First Fit algorithm combination

    Sheet2

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    49910.961071106838.0029.64

    6999.211074107047.9024.91

    8997.941077107355.0821.48

    10996.981080107660.5118.88

    Sheet2

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet3

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2998.901075107161.7012.03

    4997.941077107355.0821.48

    6997.171079107549.7329.10

    8996.541081107745.3435.36

    Sheet3

    SERIES INDEXSeries1 AvLatencytime: 4Series2 AvLatencytime :6Series3 AvLatencytime: 8Series4AvLatencytime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet4

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28216.7894494011.0731.21

    411321.7778077612.5026.47

    612422.8358157611.7424.50

    813723.50454011.0723.29

    Sheet4

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet5

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    48217.769439405.8633.04

    68217.259439408.5432.10

    88216.7894494011.0731.21

    108216.3294494013.4730.37

    Sheet5

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet6

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28219.8894193813.1218.49

    48216.7894494011.0731.21

    68214.519469429.5840.50

    88212.799489448.4447.57

    Sheet7

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29914.851068106415.9940.17

    416823.4371471015.7334.55

    620028.3927226914.3932.41

    824734.642582548.6532.31

    Sheet7

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing SSTF-First Fit algorithm combination

    Sheet8

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    49916.14106710648.6943.66

    69915.471068106412.4941.84

    89914.851068106415.9940.17

    109914.281069106519.2238.62

    Sheet8

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet9

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29918.581066106220.0125.13

    49914.851068106415.9940.17

    69912.361070106613.3150.18

    89910.591073106911.4157.31

    Sheet10

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    28218.629439391.3234.64

    411324.447807761.7629.72

    612425.495805751.4227.37

    813726.1045401.2225.86

    Sheet10

    SERIES INDEXSeries1 RRSlot = 2Series2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTime Slot vs. Performance Measures using SSTF-Best Fit algorithm combination

    Sheet11

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    48218.749439390.6634.87

    68218.789439390.9934.75

    88218.629439391.3234.64

    108218.559439401.6434.52

    Sheet11

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing SSTF-Best Fit algorithm combination

    Sheet12

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    28222.529419371.5920.94

    48218.629439391.3234.64

    68215.879459421.1244.28

    88213.839489440.9851.45

    Sheet13

    Sector Size (KB)Throughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    19914.851068106415.9940.17

    29914.851068106415.9940.17

    49914.851068106415.9940.17

    89915.231068106416.4438.58

    Sheet14

    Algorithm CombinationThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency Time

    FIFO, First Fit997.941077107355.0821.48

    FIFO, Best Fit8216.7894494011.0731.21

    SSTF, First Fit9914.851068106415.9940.17

    SSTF, Best Fit8218.629439391.3234.64

  • Disc SchedulingSample tabulated data from simulationAverage Latency Time vs. Performance Measures(for FIFO-first fit)Fixed Parameters:RR Time Slot: 2msSimulation Time: 3000msSector Size: 1KBAverage Seek Time: 8ms

  • Disc SchedulingCorresponding graph for table on previous slide

    Chart27

    99999999

    8.97.947.176.54

    1075107710791081

    1071107310751077

    61.755.0849.7345.34

    12.0321.4829.135.36

    SERIES INDEXSeries1 AvLatencytime: 2Series2 AvLatencytime :4Series3 AvLatencytime: 6Series4 AvLatencytime: 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet1

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2997.941077107355.0821.48

    416813.6671971650.8920.13

    620017.3227727447.7719.77

    824720.5126325945.9019.14

    Sheet1

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performances Measures

    RR Time Slot

    RRTimeSlot vs. Performance Measures using FIFO- First Fit algorithm combination

    Sheet2

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    49910.961071106838.0029.64

    6999.211074107047.9024.91

    8997.941077107355.0821.48

    10996.981080107660.5118.88

    Sheet2

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet3

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2998.901075107161.7012.03

    4997.941077107355.0821.48

    6997.171079107549.7329.10

    8996.541081107745.3435.36

    Sheet3

    SERIES INDEXSeries1 AvLatencytime: 2Series2 AvLatencytime :4Series3 AvLatencytime: 6Series4 AvLatencytime: 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet4

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28216.7894494011.0731.21

    411321.7778077612.5026.47

    612422.8358157611.7424.50

    813723.50454011.0723.29

    Sheet4

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet5

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    48217.769439405.8633.04

    68217.259439408.5432.10

    88216.7894494011.0731.21

    108216.3294494013.4730.37

    Sheet5

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet6

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28219.8894193813.1218.49

    48216.7894494011.0731.21

    68214.519469429.5840.50

    88212.799489448.4447.57

    Sheet7

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29914.851068106415.9940.17

    416823.4371471015.7334.55

    620028.3927226914.3932.41

    824734.642582548.6532.31

    Sheet7

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing SSTF-First Fit algorithm combination

    Sheet8

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    49916.14106710648.6943.66

    69915.471068106412.4941.84

    89914.851068106415.9940.17

    109914.281069106519.2238.62

    Sheet8

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet9

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29918.581066106220.0125.13

    49914.851068106415.9940.17

    69912.361070106613.3150.18

    89910.591073106911.4157.31

    Sheet10

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    28218.629439391.3234.64

    411324.447807761.7629.72

    612425.495805751.4227.37

    813726.1045401.2225.86

    Sheet10

    SERIES INDEXSeries1 RRSlot = 2Series2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTime Slot vs. Performance Measures using SSTF-Best Fit algorithm combination

    Sheet11

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    48218.749439390.6634.87

    68218.789439390.9934.75

    88218.629439391.3234.64

    108218.559439401.6434.52

    Sheet11

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing SSTF-Best Fit algorithm combination

    Sheet12

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    28222.529419371.5920.94

    48218.629439391.3234.64

    68215.879459421.1244.28

    88213.839489440.9851.45

    Sheet13

    Sector Size (KB)Throughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    19914.851068106415.9940.17

    29914.851068106415.9940.17

    49914.851068106415.9940.17

    89915.231068106416.4438.58

    Sheet14

    Algorithm CombinationThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency Time

    FIFO, First Fit997.941077107355.0821.48

    FIFO, Best Fit8216.7894494011.0731.21

    SSTF, First Fit9914.851068106415.9940.17

    SSTF, Best Fit8218.629439391.3234.64

  • Disc SchedulingSample tabulated data from simulationAverage Latency Time vs. Performance Measures(for SSTF-first fit)Fixed Parameters:RR Time Slot: 2msSimulation Time: 3000msSector Size: 1KBAverage Seek Time: 8ms

  • Disc SchedulingCorresponding graph for table on previous slide

    Chart29

    99999999

    18.5814.8512.3610.59

    1066106810701073

    1062106410661069

    20.0115.9913.3111.41

    25.1340.1750.1857.31

    SERIES INDEXSeries1 AvLatencytime: 2Series2 AvLatencytime :4Series3 AvLatencytime: 6Series4 AvLatencytime: 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet1

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2997.941077107355.0821.48

    416813.6671971650.8920.13

    620017.3227727447.7719.77

    824720.5126325945.9019.14

    Sheet1

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performances Measures

    RR Time Slot

    RRTimeSlot vs. Performance Measures using FIFO- First Fit algorithm combination

    Sheet2

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    49910.961071106838.0029.64

    6999.211074107047.9024.91

    8997.941077107355.0821.48

    10996.981080107660.5118.88

    Sheet2

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet3

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO FIRST FIT

    2998.901075107161.7012.03

    4997.941077107355.0821.48

    6997.171079107549.7329.10

    8996.541081107745.3435.36

    Sheet3

    SERIES INDEXSeries1 AvLatencytime: 2Series2 AvLatencytime :4Series3 AvLatencytime: 6Series4 AvLatencytime: 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using FIFO-First Fit algorithm combination

    Sheet4

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28216.7894494011.0731.21

    411321.7778077612.5026.47

    612422.8358157611.7424.50

    813723.50454011.0723.29

    Sheet4

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet5

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    48217.769439405.8633.04

    68217.259439408.5432.10

    88216.7894494011.0731.21

    108216.3294494013.4730.37

    Sheet5

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing FIFO-Best Fit algorithm combination

    Sheet6

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeFIFO BEST FIT

    28219.8894193813.1218.49

    48216.7894494011.0731.21

    68214.519469429.5840.50

    88212.799489448.4447.57

    Sheet6

    SERIES INDEXSeries1 AvLatencytime: 2Series2 AvLatencytime :4Series3 AvLatencytime: 6Series4 AvLatencytime: 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using FIFO-Best Fit algorithm combination

    Sheet7

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29914.851068106415.9940.17

    416823.4371471015.7334.55

    620028.3927226914.3932.41

    824734.642582548.6532.31

    Sheet7

    SERIES INDEXSeries 1 RRSlot = 2Series 2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTimeSlot vs. Performance Measuresusing SSTF-First Fit algorithm combination

    Sheet8

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    49916.14106710648.6943.66

    69915.471068106412.4941.84

    89914.851068106415.9940.17

    109914.281069106519.2238.62

    Sheet8

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet9

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    29918.581066106220.0125.13

    49914.851068106415.9940.17

    69912.361070106613.3150.18

    89910.591073106911.4157.31

    Sheet9

    SERIES INDEXSeries1 AvLatencytime: 2Series2 AvLatencytime :4Series3 AvLatencytime: 6Series4 AvLatencytime: 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Latency Time

    Average Latency Time vs. Performance Measures using SSTF-First Fit algorithm combination

    Sheet10

    RRTime SlotThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    28218.629439391.3234.64

    411324.447807761.7629.72

    612425.495805751.4227.37

    813726.1045401.2225.86

    Sheet10

    SERIES INDEXSeries1 RRSlot = 2Series2 RRSlot = 4Series3 RRSlot = 6Series4 RRSlot = 8

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    RRTime Slot

    RRTime Slot vs. Performance Measures using SSTF-Best Fit algorithm combination

    Sheet11

    Average Seek TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    48218.749439390.6634.87

    68218.789439390.9934.75

    88218.629439391.3234.64

    108218.559439401.6434.52

    Sheet11

    SERIES INDEXSeries1 Av.Seektime: 4Series2 Av.Seektime: 6Series3 Av.Seektime: 8Series4 Av.Seektime: 10

    PERFORMANCEMEASURES INDEX1. Throughput2. CPU Util %3. Av. Turnaround4. Av. Waiting5. %Seek time6. %Latency time

    Performance Measures

    Av. Seek Time

    Average Seek Time vs. Performance Measuresusing SSTF-Best Fit algorithm combination

    Sheet12

    Average Latency TimeThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF BEST FIT

    28222.529419371.5920.94

    48218.629439391.3234.64

    68215.879459421.1244.28

    88213.839489440.9851.45

    Sheet13

    Sector Size (KB)Throughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency TimeSSTF FIRST FIT

    19914.851068106415.9940.17

    29914.851068106415.9940.17

    49914.851068106415.9940.17

    89915.231068106416.4438.58

    Sheet14

    Algorithm CombinationThroughput% CPU UtilizationAverage Turnaround TimeAverage Waiting Time% Seek time% Latency Time

    FIFO, First Fit997.941077107355.0821.48

    FIFO, Best Fit8216.7894494011.0731.21

    SSTF, First Fit9914.851068106415.9940.17

    SSTF, Best Fit8218.629439391.3234.64

  • Disc SchedulingConclusions from the sample simulationThe average seek time and average latency time tend to inversely effect the %CPU utilization with little effect on other measures.Sector size tends to show no visible effect due to non-involvement in any of the deriving factors of the system. Increasing the time slot markedly increases the CPU utilization and throughput, and decreases the average turnaround and average waiting time. All these are indicative of the FIFO behavior. Though performance measures tend to make increased time slot look like a very lucrative proposal, associated disadvantages of possible starvation of processes apply. As the context switch decreases with increasing time quantum, so does the percentage seek and latency times. All this collectively increases the % CPU utilization.

  • Lecture SummaryIntroduction to Disc ManagementNeed for disc schedulingDisc StructureDetails of disc speedDisc Scheduling AlgorithmsParameters InvolvedParameter-Performance RelationshipsSome Sample Results

  • Preview of next lectureThe following lecture is also the last lecture. It will include concluding remarks with a summary of the main concepts studied and a parametric evaluation.