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# class15 - *computer systems preformance eval |...

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Unformatted text preview: *computer systems preformance eval | +markov/markov +- M/M/1 - kendal notation (arival/service/1 process) ++open systems ++-infinite queue +++-Fixed Rates +++-variable Rates ++-Finite Queue +++-Fixed Rates +++-Variable Rates | ++closed systems ++-Fintite +++-variable Rates | +others 1) get a word problem 2) pick a model 3) setup a model 4) solve a model consider a server for a LARGE company -it recieves requests at 50jobs/sec=lambda=uniform has 2 processors, each works at 60jobs/sec - mew is variable What is the average queue length(Nbar) SOLUTION -OPEN System -INFINITE QUEUE -Variable Rates on the test if he doesnt give a k use k=3 (P0,P1,P2) draw state transition diagram 50 50 50 50 ͻͻͻͻ Ĵ д д д п 0 1 2 3 4 ;;;; 60 120 120 120 plug into HW8.xls ------------------------------------------------------ design a computer lab customers arive at a rate 10/hour they stay an average of 50 minutes how many terminals should you have? Nbar=R*X Nbar=50min *1hour ----- *10/hour = 8.3 round up to 9 60min --------------------------------------------------------- consider a facility with 12 terminals -assume that customers who arrive when the room is full leave. what is U for the room? how many customers do you loose. -arrival 10/hour -stay an average of 50 minutes 10 10 10 10 .......................................10 ͻͻͻͻͻͻͻͻͻͻ ͻ ͻ Ĵ д д д д д д д д д Ĵ Ĵ Ŀ 0 1 2 3 4 5 6 7 8 9 10 11 12 ;;;;;;;;;;;; 6/5 2*6/5 3*6/5........................................12*6/5 lambda*P12 = loss rate plug into HW 8 ----------------------------------------------------------- Exam 2 review 1) OPEN SYSTEM 10 sec to complete arive at 4/min need to cut responsetime by half new system will take 5 sec to complete INFINITE QUEUE UNIFORM RATES draw state diagram calculate original response time --------------------------------------------------------------- 2) Closed system put numbers N=2 sec Z=5 sec lambda =?? X=?? responsetime= ?? handles 1 Req/sec .4 .2 ͻͻ Ĵ д п 0 1 2 ;; 1 1 plug into homework 7 --------------------------------------------------------------------- 3) a) littles law answer(3 terminals) b) mews = {2 4 6 6 6 6.....} use k bigger than 3 (ie 5) ...
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