I red that, process scheduler will replace the process that is currently processing by cpu with high priority process. At any point only one process will be executed by processor in that case where the scheduler is running to notify cpu about high priority process, when cpu is busy in executing low priority process ?
The process scheduler is the component of the operating system that is responsible for deciding whether the currently running process should continue running and, if not, which process should run next.
To help the scheduler monitor processes and the amount of CPU time that they use, a programmable interval timer interrupts the processor periodically (typically 50 or 60 times per second). This timer is programmed when the operating system initializes itself. At each interrupt, the operating system’s scheduler gets to run and decide whether the currently running process should be allowed to continue running or whether it should be suspended and another ready process allowed to run. This is the mechanism used for preemptive scheduling.
So,basically,the process scheduler runs in the same main memory,when active, but are only activated after getting invoked by interrupts. Hence,they aren't all time running.
BTW,that was a great conceptual question to answer.Best wishes for your topic.