Re: Devices eating too much power [was Re: Some thoughts on suspend/resume development]

Re: Devices eating too much power [was Re: Some thoughts on suspend/resume development]

[Pavel Machek]

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Hi!

> > > > This isn't to say that we should copy Windows.  However it does show that 
> > > > a very complex set of controls might not be needed.
> > 
> > Actually, as we already spindown and blank settings, we could finish
> > here :-).
> > 
> > What devices is this targetted at? Video should be handled
> > already (or perhaps we want to power down graphics card when screen is
> > blanked?). Disks spin down too. IRDA ports?
> 
> - Video

X/dpms handles these already.

> - Storage

laptop mode.

> - Hotplug devices
> - CPU power savings

cpufreq.

> - Scanner lights

Ok ;-).

> Anything you might care to imagine :>

Well, I meant something that is not already handled. Like... what
power-hungry device do we fail to properly handle today?

								Pavel
-- 
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!

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Re: Devices eating too much power [was Re: Some thoughts on suspend/resume development]

[Adam Belay]

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On Sun, 2005-03-13 at 19:14 +0100, Pavel Machek wrote:
> Hi!
> 
> > > > > This isn't to say that we should copy Windows.  However it does show that 
> > > > > a very complex set of controls might not be needed.
> > > 
> > > Actually, as we already spindown and blank settings, we could finish
> > > here :-).
> > > 
> > > What devices is this targetted at? Video should be handled
> > > already (or perhaps we want to power down graphics card when screen is
> > > blanked?). Disks spin down too. IRDA ports?
> > 
> > - Video
> 
> X/dpms handles these already.

Many GPUs will have frequency scaling like processors (e.g. ATI
Powerplay).  I don't think we currently support this.

Also we don't really control display brightness.

> > - Hotplug devices

It would be nice to lower the power state of usb and pcmcia controllers,
when these devices are also in a lower power state.

> 
> > Anything you might care to imagine :>
> 
> Well, I meant something that is not already handled. Like... what
> power-hungry device do we fail to properly handle today?

Wireless cards could be turned off when plugged into a physical media.
Many other devices remain on when not used (e.g. serial ports).
Probably most of them don't take up much power, but it would be nice to
do some experimentation and see.

I think this question really depends on architecture and hardware.
Also, I think we'll see more power management options available to us in
the near future.

Adam



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Re: Devices eating too much power [was Re: Some thoughts on suspend/resume development]

[Pavel Machek]

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Hi!

> > > > What devices is this targetted at? Video should be handled
> > > > already (or perhaps we want to power down graphics card when screen is
> > > > blanked?). Disks spin down too. IRDA ports?
> > > 
> > > - Video
> > 
> > X/dpms handles these already.
> 
> Many GPUs will have frequency scaling like processors (e.g. ATI
> Powerplay).  I don't think we currently support this.

Ugh, I did not know about this stuff. Ok.. Anyway that's X problem,
right?

> Also we don't really control display brightness.

But display brightness does not really belong here, right?

> > > Anything you might care to imagine :>
> > 
> > Well, I meant something that is not already handled. Like... what
> > power-hungry device do we fail to properly handle today?
> 
> Wireless cards could be turned off when plugged into a physical media.
> Many other devices remain on when not used (e.g. serial ports).
> Probably most of them don't take up much power, but it would be nice to
> do some experimentation and see.

I do not think wireless can be turned off when physical media is
present... but it makes sense to be user option... called ifconfig
wlan0 down. Driver should really power it down on ifconfig down.

Serial ports should not eat energy when not opened; fix it in the
driver.

What other devices do eat energy?

> I think this question really depends on architecture and hardware.
> Also, I think we'll see more power management options available to us in
> the near future.

Designing for hardware not yet available is usually bad idea.
								Pavel
-- 
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!

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Re: Devices eating too much power [was Re: Some thoughts on suspend/resume development]

[Adam Belay]

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On Sun, 2005-03-13 at 22:03 +0100, Pavel Machek wrote:
> Hi!
> 
> > > > > What devices is this targetted at? Video should be handled
> > > > > already (or perhaps we want to power down graphics card when screen is
> > > > > blanked?). Disks spin down too. IRDA ports?
> > > > 
> > > > - Video
> > > 
> > > X/dpms handles these already.
> > 
> > Many GPUs will have frequency scaling like processors (e.g. ATI
> > Powerplay).  I don't think we currently support this.
> 
> Ugh, I did not know about this stuff. Ok.. Anyway that's X problem,
> right?

Well it is now :), but many components of these X drivers should be in
the kernel.  (e.g. X does its own pci probing)

> 
> > Also we don't really control display brightness.
> 
> But display brightness does not really belong here, right?

No, in some cases it's controlled by a separate ACPI device.

> 
> > > > Anything you might care to imagine :>
> > > 
> > > Well, I meant something that is not already handled. Like... what
> > > power-hungry device do we fail to properly handle today?
> > 
> > Wireless cards could be turned off when plugged into a physical media.
> > Many other devices remain on when not used (e.g. serial ports).
> > Probably most of them don't take up much power, but it would be nice to
> > do some experimentation and see.
> 
> I do not think wireless can be turned off when physical media is
> present... but it makes sense to be user option... called ifconfig
> wlan0 down. Driver should really power it down on ifconfig down.

Fair enough.  In the typical laptop, it may be a good idea though.

> 
> Serial ports should not eat energy when not opened; fix it in the
> driver.
> 
> What other devices do eat energy?

Sound cards

bridges (PCI, PCMCIA, USB, etc.)

> > I think this question really depends on architecture and hardware.
> > Also, I think we'll see more power management options available to us in
> > the near future.
> 
> Designing for hardware not yet available is usually bad idea.

Well, not always.  For example there are PCI express specs available, so
even though not every device uses the new power management capabilities
now, we know what to expect and exactly how it will work.

Another example... ACPI spec 3.0 defines a mechanism to throttle the
performance of devices other than processors.

Adam



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Re: Devices eating too much power [was Re: Some thoughts on suspend/resume development]

[Pavel Machek]

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On Ne 13-03-05 16:55:11, Adam Belay wrote:
> On Sun, 2005-03-13 at 22:03 +0100, Pavel Machek wrote:
> > > Also we don't really control display brightness.
> > 
> > But display brightness does not really belong here, right?
> 
> No, in some cases it's controlled by a separate ACPI device.

I meant "I do not think we want to control display brightness by
runtime suspend/resume". It may be a kernel job, but not for runtime
suspend/resume. Backlight is really individual setting as much as
power managment one. Even old monitors had brightness/contrast
buttons, even if it did not spare any energy.

> > Serial ports should not eat energy when not opened; fix it in the
> > driver.
> > 
> > What other devices do eat energy?
> 
> Sound cards

Yep, hw should power them down when not opened.

> bridges (PCI, PCMCIA, USB, etc.)

Agreed, bridges are interesting. Other stuff seems to be covered.

								Pavel
-- 
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!

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Re: Devices eating too much power [was Re: Some thoughts on suspend/resume development]

[Arioch]

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Adam Belay пишет:

> Also we don't really control display brightness.

It would be good, cause on my laptop LCD's highligting lamp is 
automatically adjust after AC or battery is used.

On this laptop i had not manual control over it (i had on old Toshiba 
Tecra 550) and that hurts. Default AC brigtness is far too high :-(

As well, while on AC i'd prefer to see fancy screensaver, on battery i'd 
prefer to have waste no CPU/GPU power (no screensaver app) and turn LCD off.


I don't know of CRT's brightness has big impact on power consumption.


Of course gamma, color maps and similar funcitons belongs to X, but 
hardware, like a lamp behind LCD might be as well controlled by kernel.


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