System information

170 System Analysis and Tuning Guide
14.4.3 Kernel Configuration Options
Basic aspects of the task scheduler behavior can be set through the kernel configura-
tion options. Setting these options is part of the kernel compilation process. Because
kernel compilation process is a complex task and out of this document's scope, refer
to relevant source of information.
WARNING: Kernel Compilation
If you run SUSE Linux Enterprise Server on a kernel that was not shipped
with it, for example on a self-compiled kernel, you loose the entire support en-
titlement.
14.4.4 Terminology
Documents regarding task scheduling policy often use several technical terms which
you need to know to understand the information correctly. Here are some of them:
Latency
Delay between the time a process is scheduled to run and the actual process exe-
cution.
Granularity
The relation between granularity and latency can be expressed by the following
equation:
gran = ( lat / rtasks ) - ( lat / rtasks / rtasks )
where gran stands for granularity, lat stand for latency, and rtasks is the number
of running tasks.
14.4.4.1 Scheduling Policies
The Linux kernel supports the following scheduling policies:
SCHED_FIFO
Scheduling policy designed for special time-critical applications. It uses the First
In-First Out scheduling algorithm.