chrt与nice

chrt

NAME         
       chrt - manipulate the real-time attributes of a process
SYNOPSIS         
       chrt [options] priority command argument ...
       chrt [options] -p [priority] PID
DESCRIPTION         
       chrt sets or retrieves the real-time scheduling attributes of an
       existing PID, or runs command with the given attributes.

USAGE         
       The default behavior is to run a new command:
           chrt priority command [arguments]

       You can also retrieve the real-time attributes of an existing
       task:
           chrt -p PID

       Or set them:
           chrt -r -p priority PID

POLICIES         
       -o, --other
           Set scheduling policy to SCHED_OTHER (time-sharing
           scheduling). This is the default Linux scheduling policy.

       -f, --fifo
           Set scheduling policy to SCHED_FIFO (first in-first out).

       -r, --rr
           Set scheduling policy to SCHED_RR (round-robin scheduling).
           When no policy is defined, the SCHED_RR is used as the
           default.

       -b, --batch
           Set scheduling policy to SCHED_BATCH (scheduling batch
           processes). Linux-specific, supported since 2.6.16. The
           priority argument has to be set to zero.

       -i, --idle
           Set scheduling policy to SCHED_IDLE (scheduling very low
           priority jobs). Linux-specific, supported since 2.6.23. The
           priority argument has to be set to zero.

       -d, --deadline
           Set scheduling policy to SCHED_DEADLINE (sporadic task model
           deadline scheduling). Linux-specific, supported since 3.14.
           The priority argument has to be set to zero. See also
           --sched-runtime, --sched-deadline and --sched-period. The
           relation between the options required by the kernel is
           runtime ⇐ deadline ⇐ period. chrt copies period to deadline
           if --sched-deadline is not specified and deadline to runtime
           if --sched-runtime is not specified. It means that at least
           --sched-period has to be specified. See sched(7) for more
           details.

-o 也就是normal的情况 似乎优先级只能设置为0 输入其他的数值会出现报错

优先级和top中的显示关系

chrt输入	top里面显示
50	-1 - 50 = -51
99	rt

在top里面 RT进程都显示为优先级负数。

chrt给的优先级数值越大，优先级越高。

有效优先级：

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
SCHED_DEADLINE min/max priority : 0/0

nice

NAME         
       nice - run a program with modified scheduling priority
SYNOPSIS         
       nice [OPTION] [COMMAND [ARG]...]
DESCRIPTION         
       Run COMMAND with an adjusted niceness, which affects process
       scheduling.  With no COMMAND, print the current niceness.
       Niceness values range from -20 (most favorable to the process) to
       19 (least favorable to the process).

Niceness values range from -20 (most favorable to the process) to 19 (least favorable to the process).

19最谦让 -20最占CPU

常用参数：
-n 后面接一个数值，范围在-20~19

 nice -n -5 vi &

renice

NAME         
       renice - alter priority of running processes
SYNOPSIS         
       renice [-n] priority [-g|-p|-u] identifier...
DESCRIPTION         
       renice alters the scheduling priority of one or more running
       processes. The first argument is the priority value to be used.
       The other arguments are interpreted as process IDs (by default),
       process group IDs, user IDs, or user names. renice'ing a process
       group causes all processes in the process group to have their
       scheduling priority altered. renice'ing a user causes all
       processes owned by the user to have their scheduling priority
       altered.
OPTIONS         
       -n, --priority priority
           Specify the scheduling priority to be used for the process,
           process group, or user. Use of the option -n or --priority is
           optional, but when used it must be the first argument.

       -g, --pgrp
           Interpret the succeeding arguments as process group IDs.

       -p, --pid
           Interpret the succeeding arguments as process IDs (the
           default).

       -u, --user
           Interpret the succeeding arguments as usernames or UIDs.

       -h, --help
           Display help text and exit.

       -V, --version
           Print version and exit.

EXAMPLES         
       The following command would change the priority of the processes
       with PIDs 987 and 32, plus all processes owned by the users
       daemon and root:

       renice +1 987 -u daemon root -p 32

看起来可以修改整个用户或者进程组的nice值，以及按照加减来修改