RENICE(8) | System Manager's Manual | RENICE(8) |
renice
—
renice |
priority [[-gpu ]
who ...] ... |
renice |
-n increment
[[-gpu ] who ...]
... |
renice
alters the scheduling priority of one or more
running processes. The first argument is the new priority to apply, or if
-n
is given, the change to make (applied additively)
to the priority. This argument may be negative. (The interpretation of
priorities is discussed below.)
The following who parameters name the target
processes, as either process IDs, process group IDs, or user names. The
-gpu
options control the interpretation as
follows:
-g
-p
-u
Each who parameter is processed separately and updates the priority of the processes it names as follows:
-g
-p
-u
In conventional terminology a “high priority” process receives a lot of CPU time and a “low priority” process receives relatively little. “Niceness” is the inverse concept: a process with a high niceness level receives relatively little CPU time. It is about the process being nice to the rest of the system, rather than the system being nice to the process.
The numerical priority values accepted by
renice
are called priorities but
are actually nicenesses. They range from PRIO_MIN
(-20) to PRIO_MAX
(20).
PRIO_MIN
is the highest priority, lowest niceness,
and receives the most CPU time. PRIO_MAX
is the
lowest priority, highest niceness, and receives the least CPU time. This is
confusing but enshrined in historical practice and standards. If in doubt,
check with ps(1): processes
running with elevated priority (getting more CPU time) include
‘<’ in the FLAGS column; processes running with reduced
priority (getting less CPU time) show ‘N’ for
“nice” in FLAGS. The default priority is 0.
At priority 20, processes will specifically run only when nothing else wants to.
Users other than the super-user may only alter the priority of processes they own, and only by increasing the niceness. (This prevents overriding administrative fiats.) The super-user may alter the priority of any process to any legal value.
renice +1 987 -u daemon root -p 32
changes the priority of process ID's 987 and 32, and all processes owned by users daemon and root.
renice
command appeared in
4.0BSD.
October 22, 2020 | NetBSD 10.1 |