class18 - considder a simple example 1 cpu 2 disks (1 slow,...

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Page 1 considder a simple example 1 cpu 2 disks (1 slow, 1 fasst) -users log in and form a task and logout -at most, 2 users can be in the system at any given time -because demand is high at least 2 users are in the system -tasks alternate between a CPU and the disk -the particular disk depends on the individual job. -a typical: job uses 10 seconds of CPU time uses both disks equally uses the fast disk for 20 seconds uses the slow disk for 30 seconds Err:510 what is the performance if the system? how much would it improve if the code was rewritten? so that it ran 33% faster? what would happen if the slow disk was replaced with the fast disk? assuming original slow/fast disks, what is the optimal file placement? step 0: draw a picture MPL=2 +-----------------------+ | fastDisk ( f)| | p queue | +queue-------< >----+ CPU (1-p) queue ( s) c slowDisk c=6 /min f=3 /min s=2 /min step 1: state description use a 3-tuple "(Nc,Nf,Ns)" Nc=# @ cpu Nf=# @ fast disk Ns=# @ slow Disk Nc+Nf+Ns=2 0<Ni<=2
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This note was uploaded on 05/02/2008 for the course ECE 460 taught by Professor Michel during the Spring '08 term at UMass Dartmouth.

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class18 - considder a simple example 1 cpu 2 disks (1 slow,...

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