ionice

Run command with specific I/O class and priority

$ ionice -c [1|2|3] -n [0-7] [command]

$ ionice -c [class] -p [pid]

$ ionice -p [pid]

$ ionice -c 3 [command]

$ ionice -t -n [priority] -p [pid]

ionice [options] [command]

ionice gets or sets the I/O scheduling class and priority for a process. This controls how disk I/O requests are scheduled relative to other processes.
Scheduling classes:
- Realtime (1) - Highest priority, guaranteed I/O access (requires root)
- Best-effort (2) - Default class, shares I/O fairly based on priority
- Idle (3) - Only gets I/O time when no other process needs it

-c, --class CLASS

Scheduling class: 1 (realtime), 2 (best-effort), 3 (idle)

Priority level within class: 0 (highest) to 7 (lowest)

Apply to process with given PID

Apply to process group

Apply to all processes owned by user

Ignore failures to set priority

Only works with the CFQ (Completely Fair Queuing) I/O scheduler. Realtime class requires root privileges. BFQ and mq-deadline schedulers have different priority semantics.

ionice was introduced as part of util-linux to provide user control over the CFQ I/O scheduler's prioritization features, which were added to the Linux kernel in version 2.6.13 (2005).

nice(1), renice(1), schedtool(8)