vyznam - Make CPU Idle calls when idle

[Milan Keršláger]

On Sat, May 29, 2004 at 01:02:39PM +0200, GENTOO wrote:
> Chape nekdo vyznam tehle voleb v kernelu ?
> 
> Make CPU Idle calls when idle  CONFIG_APM_CPU_IDLE
> SW chlazeni procesoru ? Kdy se to pouziva a proc ?
> Linux preci pouziva HLT.

Asi byste mel zkusit napovedu (tj. u make config i make menuconfig), je
to tam popsano:

/usr/src/linux-2.4/Documentation/Configure.help

[...]
CONFIG_APM_CPU_IDLE
  Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
  On some machines, this can activate improved power savings, such as
  a slowed CPU clock rate, when the machine is idle. These idle calls
  are made after the idle loop has run for some length of time (e.g.,
  333 mS). On some machines, this will cause a hang at boot time or
  whenever the CPU becomes idle. (On machines with more than one CPU,
  this option does nothing.)


APM neni definovano pro SMP stroje, ale na jednoprocesorovem systemu
muzete APM aktivovat v dobe, kdy procesot "nic nedela". Z principu to
muze mit vetsi efekt, nez HLT (snizeni taktu, omezeni spotreby ostatnich
obvodu a podobne).

> Enable PM at boot time CONFIG_APM_DO_ENABLE
> Tohle uz nechapu vubec. Dokumentace veskera zadna.

CONFIG_APM_DO_ENABLE
  Enable APM features at boot time. From page 36 of the APM BIOS
  specification: "When disabled, the APM BIOS does not automatically
  power manage devices, enter the Standby State, enter the Suspend
  State, or take power saving steps in response to CPU Idle calls."
  This driver will make CPU Idle calls when Linux is idle (unless this
  feature is turned off -- see "Do CPU IDLE calls", below). This
  should always save battery power, but more complicated APM features
  will be dependent on your BIOS implementation. You may need to turn
  this option off if your computer hangs at boot time when using APM
  support, or if it beeps continuously instead of suspending. Turn
  this off if you have a NEC UltraLite Versa 33/C or a Toshiba
  T400CDT. This is off by default since most machines do fine without
  this feature.


Co se deje konkretne muzete stopovat ve zdrojakach jadra:

cd /usr/src/linux-2.4
grep -lr CONFIG_APM_CPU_IDLE .


-- 
                        Milan Kerslager
                        E-mail: milan.kerslager na pslib.cz
                        WWW:    http://www.pslib.cz/~kerslage/