Other Changes

One of the important requirements for the success of proper accounting and scheduling is the ability to keep track of time accurately. Linux uses a clock which ticks HZ times per second with HZ set as 100. This will not help us to do proper accounting of the activities since we get only a resolution of 10ms. Modern CPUs provide a timestamp counter which is incremented for every CPU clock. We have used the timestamp counter for accurately measuring the time.

Another change we have made to the Linux kernel is to the routines which insert or delete a process on the run queue. A process is inserted/deleted to/from the run-queue of the resource container to which it is bound, rather than to a global run-queue. Also whenever a process is inserted to (or deleted from) a run-queue, the runnable flag of the associated resource container is updated and this updating is propagated till the root.

Whenever a resource container is freed, the last_run array is examined and all the elements of the array pointing to the container is set to NULL.