Performance of the Scheduling Algorithm

Let us try to outline some pitfalls of the Linux scheduler. As it will turnout, some of these limitations become significant on large systems with manyusers. On a single workstation that is running a few tens of processes ata time, the Linux scheduler is quite efficient. Since Linux was born on anIntel 80386 and continues to be most popular in the PC world, we considerthe current Linux scheduler quite appropriate.

(1).The algorithm does not scale well

(2)  The predefined quantum is too large for high system loads

(3)  I/O-bound process boosting strategy is not optimal

(4)Support for real-time applications is weak

Future versions of Linux will likely address this problem, either by implementingSVR4's "fixed preemption points" or by making the kernel fully preemptive.

Issues of  Real-time Scheduler

*  kernel preemption is just one of several necessary conditions forimplementing an effective real-time scheduler.
*  real-time processes often must use resourcesalso needed by conventional processes.
*  A real-time process may thus end upwaiting until a lower-priority process releases some resource. This phenomenonis called priority inversion.
* A  real-timeprocess could require a kernel service that is granted on behalf of anotherlower-priority process (for example, a kernel thread). This phenomenon iscalled hidden scheduling.

An effective real-timescheduler should address and resolve such problems.