Linux Job Scheduler




Scheduling is a collection of wisdom and mechanisms in an operating system with regard to the sequence of the work done to your computer system.

The main purpose of the goals or the scheduling process performance optimization according to certain criteria. where the criteria for measuring and optimization of work scheduling include:
  • In order to obtain all of the jobs fair Ministry (firness).
  • In order to make the use of the processor can be maximized.
  • In order to response times can be minimized.
  • The use of resources in order to be balanced.
  • Turn arround time, time since the program entered into the system until the process is complete.
  • Efficient, the process remains in a State of busy not idle.
  • In order to make a breakthrough (thoughput) can be maximized.
1. Short-term Scheduler
Served between processor allocation scheduling processes ready in main memory the scheduling run every happening redirection process to select the next process to run.



2. Medium term scheduller
After the execution for a time, the process may delay the execution because it makes a service request input/output or calling a system call. No pending processes can make a progress towards the finish until the conditions causing delayed eliminated. In order for the memory space can be beneficial, then the process moved from main memory into memory so that the available secondary room for other processes. Main memory capacity is limited for a number of active processes. Activity transfer process that delayed from main memory to the secondary memory is called swapping. Processes have little interest when it as process delayed. But, once the conditions that make it pending lost and put back into main memory and ready.

3. Long term scheduller
This Scheduler is working against the batch queue and choose the next batch that must be executed. Is usually a batch processes with intensive use of resources (i.e. processing time, memory, input/output), these programs are a low priority, used as filler (so busy processing) during the period of activity of the job-the interactive job is low.

Use the command "at". With this command, we can do something in accordance with commands that we input based on the time that we have set. Examples in practice this time, use the ping command and using the file "try" as the storage config.

– First create the file as a command that will place configurasi used by the at command.
– And then to use the at command, use the following format "at (the desired time for scheduling.)
– input the desired command and don't forget with the inclusion of the location of a file that has been created.

Use the command "crontab". With this command, we can make scheduling 5 minutes once at once, as we want to.
– Enter a folder/etc
– and then open the file crontab command uses the nano "nano crontab"
– then at the very bottom of the table, fill the minutes in the column "m" and in the column "h" and input the date, month, year you want in the column "don" "mon" and "dow" to column "user" choose "root" as their type. And to command, you can fill it with the command that you want, but here we take an example rebboot.

Then at 20.50 my computer will restart by itself.

With this example I can deduce that the Scheduling on Linux, we can schedule some of the programs that we want to run automatically by setting the schedule according to which we want and can also be done on Ubuntu server.
 

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