linux scheduling

[rinjo]

Hi All,

What are the schedulers used in Linux?
2.6.x kernel is a preemptive kernel, but what is the type of scheduler used?

[i92guboj]

Are you speaking about i/o schedulers or task schedulers?

The task scheduler in recent kernel versions is CFS, you can start reading this:
Linux: The Completely Fair Scheduler | KernelTrap

If you meant i/o schedulers, then there are many, and you can select them on the kernel config, and even change between them as much as you want. Current kernels have three of these: anticipatory, deadline and cfq schedulers. It can also operate without an i/o scheduler.

[rinjo]

Thanks for the info.
I am talking about task schedulers.

CFS is being used in kernel above 2.6.23. But what about kernels in the 2.6.x series that came before 2.6.23?

[i92guboj]

Thanks for the info.
I am talking about task schedulers.

CFS is being used in kernel above 2.6.23. But what about kernels in the 2.6.x series that came before 2.6.23?

I don't know if the previous schedulers had a nice name like CFS, I just name them as "the linux kernel scheduler".

The scheduler for 2.4 performed at O(n), which means that the running time of the algorithm increased linearly with the number of tasks, the workload.

The 2.6 kernels do much better at O(1), which means that the algorithm should take the same to run independently of the number of tasks to schedule. This scheduler uses a round-robin algorithm to schedule the tasks with the same priority.

You might find this interesting:
http://www.google.com/url?sa=t&ct=re...PPqFl2NSqT0TCQ

[rinjo]

Thanks for the info, buddy!
Appreciated.