Re: 2.6.28 - 2.6.29-rc6-git5 regression, p4-clockmod/cpufreq probably
- From: "Rafael J. Wysocki" <rjw@xxxxxxx>
- Date: Mon, 2 Mar 2009 21:34:18 +0100
On Monday 02 March 2009, Denys Fedoryschenko wrote:
On Monday 02 March 2009 19:23:09 Sitsofe Wheeler wrote:
On Mon, Mar 02, 2009 at 06:33:46PM +0200, Denys Fedoryschenko wrote:If i will limit current in certain limits, rather than using high current, i
CPUFreq infrastructure much more powerful.
-d --min <FREQ>
new minimum CPU frequency the governor may select.
-u --max <FREQ>
new maximum CPU frequency the governor may select.
-g --governor <GOV>
new cpufreq governor.
This things you cannot do over inserting values over ACPI. Sure you can
reinvent the wheel, but why?
I guess I don't understand why you would want scaling if it didn't save
you any power...
will have in result higher efficiency of discharging battery.
The discharge curves for a Lithium Ion cell below show that the effective
capacity of the cell is reduced if the cell is discharged at very high rates
(or conversely increased with low discharge rates). This is called the
capacity offset and the effect is common to most cell chemistries.
If the discharge takes place over a long period of several hours as with some
high rate applications such as electric vehicles, the effective capacity of
the battery can be as much as double the specified capacity at the C rate.
This can be most important when dimensioning an expensive battery for high
power use. The capacity of low power, consumer electronics batteries is
normally specified for discharge at the C rate whereas the SAE uses the
discharge over a period of 20 hours (0.05C) as the standard condition for
measuring the Amphour capacity of automotive batteries. The graph below shows
that the effective capacity of a deep discharge lead acid battery is almost
doubled as the discharge rate is reduced from 1.0C to 0.05C. For discharge
times less than one hour (High C rates) the effective capacity falls off
dramatically.
This means even i need to recode on battery movie (clearly need same amount of
processing power), if i do it with 100% CPU available let's say in 30
minutes, and if i do it with 50% CPU available in 60 minutes, at the end i
should have DIFFERENT amount of remaining battery.
Another example, if i run screensaver i want governor powersave(so some crazy
flash plugin don't dry out battery till i come back) , if i run on battery i
will put conservative and limit frequency range to max 50% of CPU power, so i
can be sure my laptop lasts enough time. This in case battery time matter for
me more than computing power. Sure i will prefer some universal way, so i can
set same rules on Core 2 Duo based laptop, and cheap Celeron. Cpufreq provide
me useful framework for this job, and important SAME API everywhere. Less
efficient on p4-clockmod, and very efficient on true "mobile" processors.
* Many things quoted from http://www.mpoweruk.com/performance.htm
You should have added linux-acpi to the CC list and since the change in
question was very much on purpose, I'm not going to list (at least for now).
Thanks,
Rafael
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- References:
- 2.6.28 - 2.6.29-rc6-git5 regression, p4-clockmod/cpufreq probably
- From: Denys Fedoryschenko
- Re: 2.6.28 - 2.6.29-rc6-git5 regression, p4-clockmod/cpufreq probably
- From: Sitsofe Wheeler
- Re: 2.6.28 - 2.6.29-rc6-git5 regression, p4-clockmod/cpufreq probably
- From: Denys Fedoryschenko
- 2.6.28 - 2.6.29-rc6-git5 regression, p4-clockmod/cpufreq probably
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