CPUSPEED(8) Program Options CPUSPEED(8)NAMEcpuspeed - user-space cpu frequency scaling program, v1.5.1
SYNOPSIScpuspeed [Options]
DESCRIPTIONcpuspeed v1.5.1
This program monitors the system's idle percentage and reduces or
raises the CPUs' clock speeds and voltages accordingly to minimize
power consumption when idle and maximize performance when needed. This
is the default.
The program may also optionally be configured to reduce the CPUs' clock
speeds if the temperature gets too high, NOT minimize their speeds if
the computer's AC adapter is disconnected or maximize their speeds when
the AC adapter is connected.
By default this program will manage every CPU found in the system.
Options:
-d
Tells the process to daemonize itself (run in background).
-i <interval>
Sets the interval between idle percentage tests and possible
speed changes in tenths of a second (default is 20).
-p <fast up> <threshold>
Sets the CPU core idle percentage thresholds. <fast up> is the
idle percentage below which a CPU core will be set to the high‐
est possible speed. <threshold> is the idle percentage above
which a CPU core's speed will be decreased and below which a CPU
core's speed will be increased (defaults are 10 and 25).
-m <minimum speed>
Sets the minimum speed in KHz below which a CPU core will not be
set.
-M <maximum speed>
Sets the maximum speed in KHz above which a CPU core will not be
set.
-n
Do not treat niced programs as idle time.
-w
Do not treat time waiting for IO as idle time.
-t <temp file> <maxtemp>
Sets the ACPI temperature file and the temperature at which CPUs
will be set to minimum speed.
-T <interval>
Sets the interval at which the temperature will be polled in
tenths of a second (default is 10). (Requires the '-t' option
above.)
-a <AC file>
Sets the ACPI AC adapter state file and tells the program to set
the CPUs to minimum speed when the AC adapter is disconnected.
(This is the default but is changeable by the '-D' option
below).
-A <interval>
Sets the interval at which the AC adapter state will be polled
in tenths of a second (default is 50). (Requires the '-a'
option above.)
-C
Run at maximum speed when AC adapter is connected. (Requires
the '-a' option above.)
-D
Do NOT force minimum speed when AC adapter is disconnected.
(Requires the '-a' option above.)
-r
Restores previous speed on program exit.
-S <CPU core 1> [[<CPU core 2>] ...]
Manage only a single group of CPU cores. All of the specified
cores will controlled as a single group (locked to the same
speed) and are in the range 0 to n-1 where 'n' is the total num‐
ber of CPU cores in the system. Note that when specifying mul‐
tiple cores the list must be enclosed in quotes. Without this
option the program creates copies of itself to manage every core
of every CPU in the system and automatically determines core
groups. If you are running on an old kernel and get an error
message about not being able to open an "affected_cpus" file
then you must run this program separately for each group of
cores that must be controlled together (which probably means for
each physical CPU) and use this option.
Notes:
To have a CPU core stay at the highest clock speed to maximize perfor‐
mance send the process controlling that CPU core the SIGUSR1 signal.
To have a CPU core stay at the lowest clock speed to maximize battery
life send the process controlling that CPU core the SIGUSR2 signal.
To resume having a CPU core's clock speed dynamically scaled send the
process controlling that CPU core the SIGHUP signal.
Many modern Linux systems support in-kernel cpu frequency scaling. The
cpuspeed daemon only works in conjunction with the 'userspace' fre‐
quency scaling governor. Other governors, such as 'ondemand' and 'con‐
servative', rely on the Linux kernel to adjust cpu frequencies on the
fly without the need of any user-space assistance, such as that pro‐
vided by cpuspeed.
Red Hat and Fedora distributions employ a unified configuration file
for both scenarios, as well as a cpuspeed init script that will config‐
ure either cpuspeed or in-kernel cpu frequency scaling, as appropriate.
FILES
/etc/sysconfig/cpuspeed, configuration file
/etc/init.d/cpuspeed, initialzation script
/usr/sbin/cpuspeed, cpuspeed program
SEE ALSO
The CPUSpeed web page:
http://carlthompson.net/Software/CPUSpeed
LICENSE
CPUSpeed is released under the GNU General Public License version 2 (or
if you wish any later version). This license allows you to use, copy,
distribute and modify the software with very few restrictions. The full
text of the license may be found here:
http://carlthompson.net/Software/CPUSpeed/License
AUTHOR(S):
CPUSpeed daemon, original init script and configuration file:
Carl Thompson - cet [at] carlthompson.net
(copyright 2002 - 2008)
Modernized init script, configuration file and man page:
Dave Jones - davej [at] redhat.com
Michal Jaegermann - michal [at] harddata.com
Jarod Wilson - jwilson [at] redhat.com
cpuspeed v1.5.1 October 08, 2008 CPUSPEED(8)
