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Tuning the Task Scheduler 171

SCHED_BATCH

Scheduling policy designed for CPU-intensive tasks.

SCHED_IDLE

Scheduling policy intended for very low prioritized tasks.

SCHED_OTHER

Default Linux time-sharing scheduling policy used by the majority of processes.

SCHED_RR

Similar to SCHED_FIFO, but uses the Round Robin scheduling algorithm.

14.4.5 Changing Real-time Attributes

ofProcesses with chrt

The chrt command sets or retrieves the real-time scheduling attributes of a running

process, or runs a command with the specified attributes. You can get or retrieve both

the scheduling policy and priority of a process.

In the following examples, a process whose PID is 16244 is used.

To retrieve the real-time attributes of an existing task:

saturn.example.com:~ # chrt -p 16244

pid 16244's current scheduling policy: SCHED_OTHER

pid 16244's current scheduling priority: 0

Before setting a new scheduling policy on the process, you need to find out the mini-

mum and maximum valid priorities for each scheduling algorithm:

saturn.example.com:~ # chrt -m

SCHED_OTHER min/max priority : 0/0

SCHED_FIFO min/max priority : 1/99

SCHED_RR min/max priority : 1/99

SCHED_BATCH min/max priority : 0/0

SCHED_IDLE min/max priority : 0/0

In the above example, SCHED_OTHER, SCHED_BATCH, SCHED_IDLE polices

only allow for priority 0, while that of SCHED_FIFO and SCHED_RR can range

from 1 to 99.

To set SCHED_BATCH scheduling policy:

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Red Hat ENTERPRISE LINUX 5.4 - SYSTEMTAP BEGINNERS GUIDE Informazioni Techniche Pagina 185