cpuanddiskschedulingalgorithms(參考版)
2024-10-03 21:50本頁面
【正文】 the base level queue. Escaping to a Higher Level Queue 1 Queue 2 Queue 3 (round robin) RUN WAIT Vista ? The scheduler was modified to keep track of how many cycles a thread has gone through. ? There is also now a priority scheduler for the I/O queue. ? This makes sure that background tasks don’t interfere with foreground tasks. Linux ? Up to version Linux also used the multilevel feedback queue. ? The differences however were: ? Priorities ranged from 0 – 140 ? 0 – 99 belong to real time tasks ? 100 – 140 are for “nice” task levels Nice ? Is a program that maps directly to the kernel. ? Nice assigns priority from lowest being 19 to highest being 20. ? The usual default is 0 ? Assigning priorities is done through various heuristics of the scheduler. Linux Scheduler ? The quantum time is time allowed for a process ? The real time processes in Linux have a quantum time of 200 ms, nice processes have 10 ms. ? The scheduler runs through the queue allowing the highest priority tasks to go first. Linux Scheduler cont. ? Once a process has used its allotted amount of time it is put into an expired queue. ? When the active queue is empty then the expired queue bees the active queue. Linux Version ? This version is a little different than the previous one. ? This version used a O(1) Scheduler. ? The big “O” notations was used not because this scheduler is that fast, but to represent that no matter how many processes there are it will take the same amount of time to schedule them. Linux version ? In this version the Completely Fair Scheduler was introduc
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