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home | helpx minix x x minixx IONICE(1) User Commands IONICE(1) NAME ionice - set or get process I/O scheduling class and priority SYNOPSIS ionice [-c class] [-n level] [-t] -p PID... ionice [-c class] [-n level] [-t] -P PGID... ionice [-c class] [-n level] [-t] -u UID... ionice [-c class] [-n level] [-t] command [argument...] DESCRIPTION This program sets or gets the I/O scheduling class and priority for a program. If no arguments or just -p is given, ionice will query the current I/O scheduling class and priority for that process. When command is given, ionice will run this command with the given ar- guments. If no class is specified, then command will be executed with the "best-effort" scheduling class. The default priority level is 4. As of this writing, a process can be in one of three scheduling classes: Idle A program running with idle I/O priority will only get disk time when no other program has asked for disk I/O for a defined grace period. The impact of an idle I/O process on normal system ac- tivity should be zero. This scheduling class does not take a priority argument. Presently, this scheduling class is permit- ted for an ordinary user (since kernel 2.6.25). Best-effort This is the effective scheduling class for any process that has not asked for a specific I/O priority. This class takes a pri- ority argument from 0-7, with a lower number being higher prior- ity. Programs running at the same best-effort priority are served in a round-robin fashion. Note that before kernel 2.6.26 a process that has not asked for an I/O priority formally uses "none" as scheduling class, but the I/O scheduler will treat such processes as if it were in the best-effort class. The priority within the best-effort class will be dynamically derived from the CPU nice level of the process: io_priority = (cpu_nice + 20) / 5. For kernels after 2.6.26 with the CFQ I/O scheduler, a process that has not asked for an I/O priority inherits its CPU schedul- ing class. The I/O priority is derived from the CPU nice level of the process (same as before kernel 2.6.26). Realtime The RT scheduling class is given first access to the disk, re- gardless of what else is going on in the system. Thus the RT class needs to be used with some care, as it can starve other processes. As with the best-effort class, 8 priority levels are defined denoting how big a time slice a given process will re- ceive on each scheduling window. This scheduling class is not permitted for an ordinary (i.e., non-root) user. OPTIONS -c, --class class Specify the name or number of the scheduling class to use; 0 for none, 1 for realtime, 2 for best-effort, 3 for idle. -n, --classdata level Specify the scheduling class data. This only has an effect if the class accepts an argument. For realtime and best-effort, 0-7 are valid data (priority levels), and 0 represents the high- est priority level. -p, --pid PID... Specify the process IDs of running processes for which to get or set the scheduling parameters. -P, --pgid PGID... Specify the process group IDs of running processes for which to get or set the scheduling parameters. -t, --ignore Ignore failure to set the requested priority. If command was specified, run it even in case it was not possible to set the desired scheduling priority, which can happen due to insuffi- cient privileges or an old kernel version. -h, --help Display help text and exit. -u, --uid UID... Specify the user IDs of running processes for which to get or set the scheduling parameters. -V, --version Display version information and exit. EXAMPLES # ionice -c 3 -p 89 Sets process with PID 89 as an idle I/O process. # ionice -c 2 -n 0 bash Runs 'bash' as a best-effort program with highest priority. # ionice -p 89 91 Prints the class and priority of the processes with PID 89 and 91. NOTES Linux supports I/O scheduling priorities and classes since 2.6.13 with the CFQ I/O scheduler. AUTHORS Jens Axboe <jens@axboe.dk> Karel Zak <kzak@redhat.com> SEE ALSO ioprio_set(2) AVAILABILITY The ionice command is part of the util-linux package and is available from https://www.kernel.org/pub/linux/utils/util-linux/. util-linux July 2011 IONICE(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | NOTES | AUTHORS | SEE ALSO | AVAILABILITY