cpuanddiskschedulingalgorithms

cpuanddiskschedulingalgorithms内容摘要：

owed 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 introduced. It runs on the idea of giving the task with the “gravest need” to the CPU  This method uses what is called a red black tree instead of queues. The Red Black Tree This is a type of Binary Search Tree. With a few differences. • First, a node is either black or red. • Second, the root is black. •Third, all leaves are black •Fourth, both children of every node are black •Fifth, Every simple path from a given node to any of its descendant leaves contains the same number of black nodes. So what does this all mean?  No path can have two red nodes in a row.  The shortest possible path has all black nodes, and the longest possible path alternates between red and black nodes.  Since all maximal paths have the same number of black nodes, this shows that no path is more than twice as long as any other path.。