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developersguide:userspacescheduling [2014/11/11 08:52]
127.0.0.1 external edit
developersguide:userspacescheduling [2017/06/02 10:26]
shtjonathan [How does it work?]
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 ==== How does it work? ==== ==== How does it work? ====
-Scheduling in Minix is simple multi-priority round robin. Each runnable ​processes ​in a its priority queue and has a quantum assigned. The assigned quantum of each process is periodically decreased. Each process is associated with a scheduler, e.g. a process that is responsible for making scheduling decisions for such a process.+Scheduling in Minix is simple multi-priority round robin. Each runnable ​process is in a priority queue and has a quantum assigned. The assigned quantum of each process is periodically decreased. Each process is associated with a scheduler, e.g. a process that is responsible for making scheduling decisions for such a process.
  
-The //kernel// retains a very simple round robin scheduler which always picks the process at the head of the highest priority queue. This does not guarantee that processes will not starve. It also contain ​a default policy. If a process is not associated with any userspace scheduler and runs out of its quantum the quantum is renewed. If a process is associated with a scheduler a message generated by the kernel on behalf of the process is sent to the scheduler every time the process runs out of its quantum. ​Process ​that runs out of its quantum is blocked (not runnable) until the scheduler decides.+The //kernel// retains a very simple round robin scheduler which always picks the process at the head of the highest priority queue. This does not guarantee that processes will not starve. It also contains ​a default policy. If a process is not associated with any userspace scheduler and runs out of its quantumthe quantum is renewed. If a process is associated with a schedulera message generated by the kernel on behalf of the process is sent to the scheduler every time the process runs out of its quantum. ​A process ​that runs out of its quantum is blocked (not runnable) until the scheduler decides.
  
 The scheduler can change the process priority and time quantum. //​sys_schedule()//​ is used to change the priority and quantum and thus can make the process runnable again. The scheduler can change the process priority and time quantum. //​sys_schedule()//​ is used to change the priority and quantum and thus can make the process runnable again.
  
-The userspace scheduler can use  //​sef_receive_status() //to check whether the message was generated by the kernel or whether the massage is a fake sent by a processes. This information is reliable.+The userspace scheduler can use  //​sef_receive_status()//​ to check whether the message was generated by the kernel or whether the massage is a fake sent by a process. This information is reliable.
  
 ==== Advantages over the in-kernel scheduler ==== ==== Advantages over the in-kernel scheduler ====
developersguide/userspacescheduling.txt · Last modified: 2017/06/02 10:31 by shtjonathan