Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
powerd++(8)		  BSD System Manager's Manual		   powerd++(8)

NAME
     powerd++ -- CPU clock speed daemon

SYNOPSIS
     powerd++ -h
     powerd++ [-vf] [-a	mode] [-b mode]	[-n mode] [-m freq] [-M	freq]
	      [-p ival]	[-s cnt] [-P file]

DESCRIPTION
     The powerd++ daemon monitors the system load and adjusts the CPU clock
     speed accordingly.	 It is a drop-in replacement for powerd(8) and sup-
     ports two modes of	operation, a load feedback control loop	or fixed fre-
     quency operation.

   ARGUMENTS
     The following argument types can be given:

     mode    The mode is either	a load target or a fixed freq.	The powerd(8)
	     modes are interpreted as follows:
	     maximum, max
		     Use the highest clock frequency.
	     minimum, min
		     Use the lowest clock frequency.
	     adaptive, adp
		     A target load of 0.5 (50%).
	     hiadaptive, hadp
		     A target load of 0.375 (37.5%).

	     If	a scalar number	is given, it is	interpreted as a load.

     load    A load is either a	fraction in the	range [0.0, 1.0] or a percent-
	     age in the	range [0%, 100%].

     freq    A clock frequency consists	of a number and	a frequency unit.
		   Hz, KHz, MHz, GHz, THz
	     The unit is not case sensitive, if	omitted	MHz are	assumed	for
	     compatibility with	powerd(8).

     ival    A time interval can be given in seconds or	milliseconds.
		   s, ms
	     An	interval without a unit	is treated as milliseconds.

     cnt     A positive	integer.

     file    A file name.

   OPTIONS
     The following options are supported:

     -h, --help
	     Show usage	and exit

     -v, --verbose
	     Be	verbose	and produce initial diagnostics	on stderr.

     -f, --foreground
	     Stay in foreground, produce an event log on stdout.

     -a, --ac mode
	     Mode to use while the AC power line is connected (default hadp).

     -b, --batt	mode
	     Mode to use while battery powered (default	adp).

     -n, --unknown mode
	     Mode to use while the power line state is unknown (default	hadp).

     -m, --min freq
	     The lowest	CPU clock frequency to use (default 0Hz).

     -M, --max freq
	     The highest CPU clock frequency to	use (default 1THz).

     --min-ac freq
	     The lowest	CPU clock frequency to use on AC power.

     --max-ac freq
	     The highest CPU clock frequency to	use on AC power.

     --min-batt	freq
	     The lowest	CPU clock frequency to use on battery power.

     --max-batt	freq
	     The highest CPU clock frequency to	use on battery power.

     -p, --poll	ival
	     The polling interval that is used to take load samples and	update
	     the CPU clock (default 0.5s).

     -s, --samples cnt
	     The number	of load	samples	to use to calculate the	current	load.
	     The default is 4.

     -P, --pid file
	     Use an alternative	pidfile, the default is	/var/run/powerd.pid.
	     The default ensures that powerd(8)	and powerd++ are not run si-
	     multaneously.

     -i, -r load
	     Legacy arguments from powerd(8) not applicable to powerd++	and
	     thus ignored.

SERVICE
     The powerd++ daemon can be	run as an rc(8)	service. Add the following
     line to rc.conf(5):
	   powerdxx_enable="YES"
     Command line arguments can	be set via powerdxx_flags.

TOOLS
     The loadrec(1) and	loadplay(1) tools offer	the possibility	to record sys-
     tem loads and replay them.

IMPLEMENTATION NOTES
     This section describes the	operation of powerd++.

     Both powerd(8) and	powerd++ have in common, that they work	by polling
     kern.cp_times via sysctl(3), which	is an array of the accumulated loads
     of	every core. By subtracting the last cp_times sample the	loads over the
     polling interval can be determined. This information is used to set a new
     CPU clock frequency by updating dev.cpu.0.freq.

   Initialisation
     After parsing command line	arguments powerd++ assigns a clock frequency
     controller	to every core. I.e. cores are grouped by a common
     dev.cpu.%d.freq handle that controls the clock for	all of them. Due to
     limitations of cpufreq(4) dev.cpu.0.freq is the controlling handle	for
     all cores,	even across multiple CPUs. However powerd++ is not built with
     that assumption and per CPU, core or thread controls will work as soon as
     the hardware and kernel support them.

     In	the next initialisation	stage the available frequencies	for every core
     group are determined to set appropriate lower and upper boundaries. This
     is	a purely cosmetic measure and used to avoid unnecessary	frequency up-
     dates. The	controlling algorithm does not require this information, so
     failure to	do so will only	be reported (non-fatally) in verbose mode.

   Detaching From the Terminal
     After the initialisation phase powerd++ prepares to detach	from the ter-
     minal. The	first step is to acquire a lock	on the pidfile.	Afterwards all
     the frequencies are read and written as a last opportunity	to fail. After
     detaching from the	terminal the pidfile is	written	and the	daemon goes
     into frequency controlling	operation until	killed by a signal.

   Load	Control	Loop
     The original powerd(8) uses a hysteresis to control the CPU frequency.
     I.e. it determines	the load over all cores	since taking the last sample
     (the summary load during the last polling interval) and uses a lower and
     an	upper load boundary to decide whether it should	update the frequency
     or	not.

     powerd++ has some core differences. It can	take more than two samples
     (four by default),	this makes it more robust against small	spikes in
     load, while retaining much	of its ability to quickly react	to sudden sur-
     ges in load.  Changing the	number of samples does not change the runtime
     cost of running powerd++.

     Instead of	taking the sum of all loads, the highest load within the core
     group is used to decide the next frequency	target.	Like with powerd(8)
     this means, that high load	on a single core will cause an increase	in the
     clock frequency. Unlike powerd(8) it also means that moderate load	over
     all cores allows a	decrease of the	clock frequency.

     The powerd++ daemon steers	the clock frequency to match a load target,
     e.g. if there was a 25% load on 2 GHz and the load	target was 50%,	the
     frequency would be	set to 1 GHz.

   Termination and Signals
     The signals HUP and TERM cause an orderly shutdown	of powerd++.  An or-
     derly shutdown means the pidfile is removed and the clock frequencies are
     restored to their original	values.

FILES
     /var/run/powerd.pid Common	pidfile	with powerd(8).
     /usr/local/etc/rc.d/powerdxx Service file,	enable in rc.conf(5).

EXAMPLES
     Run in foreground,	minimum	clock frequency	800 MHz:
	   powerd++ -fm800

     Report configuration before detaching into	the background:
	   powerd++ -v

     Target 75%	load on	battery	power and run at 2.4 GHz on AC power:
	   powerd++ -b .75 -a 2.4ghz

     Target 25%	load on	AC power:
	   powerd++ -a 25%

     Use the same load sampling	powerd(8) does:
	   powerd++ -s2	-p.25s

DIAGNOSTICS
     The powerd++ daemon exits 0 on receiving an INT or	TERM signal, and >0 if
     an	error occurs.

COMPATIBILITY
     So	far powerd++ requires ACPI to detect the current power line state.

SEE ALSO
     cpufreq(4), powerd(8), loadrec(1),	loadplay(1)

AUTHORS
     Implementation and	manual by Dominic Fandrey <kami@freebsd.org>

BSD			       19 October, 2016				   BSD

NAME | SYNOPSIS | DESCRIPTION | SERVICE | TOOLS | IMPLEMENTATION NOTES | FILES | EXAMPLES | DIAGNOSTICS | COMPATIBILITY | SEE ALSO | AUTHORS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=powerdxx&manpath=FreeBSD+12.1-RELEASE+and+Ports>

home | help