66
Chapter 6
Give this a try on a process you have currently running and then run
ps
to see how it changes, if at all.
Changing the Priority of a Running Process with renice
The
renice
command takes absolute values between –20 and 19 and sets
the priority
to that particular level, rather than increasing or decreasing
from the level at which it started. In addition,
renice
requires the PID of the
process you are targeting rather than the name. So, if
slowprocess
is using
an inordinate amount of resources on your system
and you want to give it
a lower priority, thus allowing other processes a higher priority and more
resources, you could
renice
the
slowprocess
(which has a PID of 6996) and
give it a much higher
nice
value, like so:
kali >
renice 19 6996
As with
nice
, only the root user can
renice
a
process to a negative value
to give it higher priority, but any user can be nice and reduce priority with
renice
.
You can also use the
top
utility to change the
nice
value. With the
top
utility running, simply press the R key and
then supply the PID and the
nice
value. Listing 64 shows the
top
utility running. When I press the R key and
supply the PID and
nice
value, I get the following output:
top - 21:36:56 up 21:41, 2 users, load average: 0.60, 0.22, 0.11
Tasks: 128 total, 1 running, 127 sleeping, 0 stopped, 0 zombie
%Cpu(s): 1.5 us, 0.7 sy, 0.0 ni, 96.7 id, 1.1 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem: 511864 total, 500780 used, 11084 free, 152308 buffers
KiB Swap: 901116 total, 14444 used, 886672 free, 171376 cached
u
PID to renice
|
PID USER PR NI VIRT RES SHR S %CPU %MEM
TIME COMMAND
5451 root 20 0 1577m 19m 14m S 5.3 3.9 42:46.26 0LLYDBG.EXE
2766 root 20 0 55800 20m 5480 S 2.6 4.0 1:01.42 Xorg
5456 root 20 0 6356 4272 1780 S 1.3 0.8 13:21.69 wineserver
7 root 20 0 0 0 0 S 0.3 0.0 0:30.12 rcu_sched
5762 root 20 0 174m 20m 17m S 0.3 4.1 0:04.74 gnome-terminal
Listing 6-4: Changing a nice value when top is in use
When I press the R key, I’m asked
for the PID u with the text
renice
PID [value] to value
. The output should then change to reflect the new
priorities.
