Thread Scheduler Details

The adaptive partitioning thread scheduler is an optional thread scheduler that lets you guarantee minimum percentages of the CPU's throughput to groups of threads, processes, or applications. The percentage of the CPU allotted to a partition is called a budget.

The thread scheduler was designed on top of the core QNX Neutrino RTOS architecture to primarily solve two problems in embedded systems design:

• to function properly under fully loaded conditions
• to prevent unimportant or untrusted applications from monopolizing the system

We call our partitions adaptive because their contents are dynamic:

• You can dynamically launch an application into a partition.
• Child threads and child processes automatically run in the same partition as the creating thread.
• By default, when you use the standard QNX Neutrino send-receive-reply messaging, message receivers automatically run in the partition of the message sender while they're processing that message. This means that all resource managers, such as drivers and filesystems, automatically bill CPU time (except overhead) to the budget of their clients.

You can control adaptive partitioning from the command line with the aps utility (see the Utilities Reference), or from a program with the SchedCtl() or SchedCtl_r() function (see the QNX Neutrino C Library Reference).