Linux Operating system principles

Linux: Process preemption, preemption based on time interruption
System clock: Internal clock frequency, resulting in clock interrupts
TICK: Time resolution, number of interrupts Hz

100Hz 100 times per second interrupt
1000Hz
Every tick produces a clock break that can be robbed.
A:5MS, 1ms
C:

Process Category:
Interactive process (I/O)
Batch process (CPU)
Real-time process (real-time), immediate response, highest priority

CPU intensive (Batch process): Long time slices, low priority
IO-intensive (interactive process): Short time slices, high priority

[Email protected] ~]# ps-e-o class,rtprio,nice,pri,nice,cmd
CLS rtprio ni PRI ni CMD
TS (Other)-0 0/sbin/init
TS-0 0 [Kthreadd] usually parentheses are kernel threads
FF (FIFO) 99-139-[migration/0]
TS-0 0 [ksoftirqd/0]
FF 99-139-[migration/0]

Liunx Precedence: Priority
Real-time Priority: 1-99, the smaller the number, the lower the priority level
Static priority: 100-139, the smaller the number, the higher the priority

Nice value-20 to 19, corresponding to 100 to 139,nice value of 0 for 120, default = 0
Real-time priority with high static priority level

Nice value: Adjust the static priority level

scheduling category;
Real-time processes:
SCHED Fifo:first in first out scheduling FIFO process
Sched_rr:round Robin scheduling RR's real-time scheduling process
Sched_other: A process that is dedicated to scheduling user-space processes between 100-139

More than 2 of Red Hat 6:

Sched_batch Scheduling Batch Processes

Sched_idle Scheduling Idle Processes

Dynamic Priority:
Temporary high priority, mainly to 100-139 of the process, the user space process, long time did not get time slices or long time to obtain time slices, to adjust
Dynamic priority = MAX (100,min (static Priority-bonus + 5,139)) is equal to 100 and min (static Priority-bonus + 5,139) Maximum number

Bonus (range 10 to 10)

For example, after 110 of the priority penalty for Level 3 measures
110-(-3) +5 =118
Equals 118

To manually adjust the process priority level:

100-139:nice value

Nice N COMMAND

Renice-n Specify a new nice value to specify the PID number

1-99:

Chrt:

-P Specify PID

-F Specify FIFO category

-R Specify RR category

-b Specifies the batch process

-I idle Process

Chrt-f-P [Prio] PID tuning FIFO priority

Chrt-r-P [Prio] PID adjusts RR priority

Chrt-f-P [prio] command to specify priority when command is started

PS-E-o class,rtprio,nice,pri,nice,cmd view command

chrt-p [Prio] COMMAND adjusts the priority of the 100-139 process

This article from "Operation and maintenance Growth Road" blog, declined reprint!

Linux Operating system principles