* Re: CONFIG_SUSPEND and power consumption [not found] <20070819153259.2c96b904@hyperion.delvare> @ 2007-08-19 20:42 ` Rafael J. Wysocki 2007-08-20 10:02 ` Jean Delvare 0 siblings, 1 reply; 8+ messages in thread From: Rafael J. Wysocki @ 2007-08-19 20:42 UTC (permalink / raw) To: Jean Delvare; +Cc: LKML Hi, On Sunday, 19 August 2007 15:32, Jean Delvare wrote: > Hi all, hi Rafael, > > Running kernel 2.6.23-rc3-git1, I noticed yesterday that my CPU (AMD > Sempron 2600+) was running at a much lower temperature when > CONFIG_SUSPEND was enabled. Hm, interesting. > The temperature difference was quite significant, about 6 degrees Celsius at > idle. Measuring the power consumption of my system confirmed that the energy > savings were real: with CONFIG_SUSPEND=n, the system consumes 80 W of power > (idle), while with CONFIG_SUSPEND=y, the system consumes only 69 W (idle)! > Can anyone explain how this works? I can't. > I didn't expect CONFIG_SUSPEND to make any difference before actually > switching the system to standby or suspend state. Yes, that's the expected behavior. > I tried the same trick on two Intel motherboards I use for testing, but > this option didn't seem to make any difference in the power consumption > for these. Do you have CONFIG_HIBERNATION set? If not, please see if setting it instead of CONFIG_SUSPEND leads to the same result on the affected box (ie. running at lower temperatures). Greetings, Rafael ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: CONFIG_SUSPEND and power consumption 2007-08-19 20:42 ` CONFIG_SUSPEND and power consumption Rafael J. Wysocki @ 2007-08-20 10:02 ` Jean Delvare 2007-08-20 10:11 ` Oliver Neukum 0 siblings, 1 reply; 8+ messages in thread From: Jean Delvare @ 2007-08-20 10:02 UTC (permalink / raw) To: Rafael J. Wysocki; +Cc: LKML Hi Rafael, On Sun, 19 Aug 2007 22:42:43 +0200, Rafael J. Wysocki wrote: > On Sunday, 19 August 2007 15:32, Jean Delvare wrote: > > Hi all, hi Rafael, > > > > Running kernel 2.6.23-rc3-git1, I noticed yesterday that my CPU (AMD > > Sempron 2600+) was running at a much lower temperature when > > CONFIG_SUSPEND was enabled. > > Hm, interesting. > > > The temperature difference was quite significant, about 6 degrees Celsius at > > idle. Measuring the power consumption of my system confirmed that the energy > > savings were real: with CONFIG_SUSPEND=n, the system consumes 80 W of power > > (idle), while with CONFIG_SUSPEND=y, the system consumes only 69 W (idle)! > > Can anyone explain how this works? > > I can't. > > > I didn't expect CONFIG_SUSPEND to make any difference before actually > > switching the system to standby or suspend state. > > Yes, that's the expected behavior. > > > I tried the same trick on two Intel motherboards I use for testing, but > > this option didn't seem to make any difference in the power consumption > > for these. > > Do you have CONFIG_HIBERNATION set? If not, please see if setting it instead > of CONFIG_SUSPEND leads to the same result on the affected box (ie. running > at lower temperatures). I've made some more tests. More importantly, the additional power consumption comes from my (new) external hard disk drive. When it's not connected, the system consume 69 W at idle, regardless of the config options. I guess that the drive was being autosuspended (by CONFIG_USB_SUSPEND) only when CONFIG_SUSPEND was set. But as I found that my drive never comes back from autosuspend, it's now blacklisted, and my system consumes 80 W again even with CONFIG_SUSPEND=y. If I rmmod "ehci-hcd" then the power consumption is back to 69 W. This confirms that this is really USB-related. I have to admit that I did not expect an external drive to eat that much power from the system, especially when not used. I am told that VIA chips are notoriously bad at this kind of things. I'll try the same external drive on an Intel system later today. The last mystery remaining is how USB "activity" can cause my CPU to heat. I would expect the south bridge to heat, not the CPU. Thanks, -- Jean Delvare ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: CONFIG_SUSPEND and power consumption 2007-08-20 10:02 ` Jean Delvare @ 2007-08-20 10:11 ` Oliver Neukum 2007-08-20 15:34 ` Jean Delvare 2007-08-20 17:29 ` Pavel Machek 0 siblings, 2 replies; 8+ messages in thread From: Oliver Neukum @ 2007-08-20 10:11 UTC (permalink / raw) To: Jean Delvare; +Cc: Rafael J. Wysocki, LKML Am Montag 20 August 2007 schrieb Jean Delvare: > If I rmmod "ehci-hcd" then the power consumption is back to 69 W. This > confirms that this is really USB-related. I have to admit that I did > not expect an external drive to eat that much power from the system, > especially when not used. I am told that VIA chips are notoriously bad > at this kind of things. I'll try the same external drive on an Intel > system later today. > > The last mystery remaining is how USB "activity" can cause my CPU to > heat. I would expect the south bridge to heat, not the CPU. USB, or strictly speaking EHCI, OHCI and UHCI, use DMA. To allow that the cache coherency logic has to be active. Therefore your CPU cannot go to C3. Therefore it draws more power. The problem we are facing in USB is that to get great savings, our coverage has to be perfect. One device that cannot be autosuspended and we lose most savings. Regards Oliver ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: CONFIG_SUSPEND and power consumption 2007-08-20 10:11 ` Oliver Neukum @ 2007-08-20 15:34 ` Jean Delvare 2007-08-20 17:29 ` Pavel Machek 1 sibling, 0 replies; 8+ messages in thread From: Jean Delvare @ 2007-08-20 15:34 UTC (permalink / raw) To: Oliver Neukum; +Cc: Rafael J. Wysocki, LKML On Mon, 20 Aug 2007 12:11:34 +0200, Oliver Neukum wrote: > Am Montag 20 August 2007 schrieb Jean Delvare: > > If I rmmod "ehci-hcd" then the power consumption is back to 69 W. This > > confirms that this is really USB-related. I have to admit that I did > > not expect an external drive to eat that much power from the system, > > especially when not used. I am told that VIA chips are notoriously bad > > at this kind of things. I'll try the same external drive on an Intel > > system later today. > > > > The last mystery remaining is how USB "activity" can cause my CPU to > > heat. I would expect the south bridge to heat, not the CPU. > > USB, or strictly speaking EHCI, OHCI and UHCI, use DMA. To allow > that the cache coherency logic has to be active. Therefore your CPU > cannot go to C3. Therefore it draws more power. The problem we are > facing in USB is that to get great savings, our coverage has to be perfect. > One device that cannot be autosuspended and we lose most savings. Ah, OK, thanks for the clarification, it explains a lot. I've made some more tests on two Intel boards and another VIA board. The bottom line is that both VIA boards see a bump in power consumption when plugging my USB 2.0 hard disk drive (10 W on one board, 4 W on the other) while none of the Intel boards exhibit any change in power consumption. I wonder if I should blame VIA for eating extra power when the disk is plugged, or thank them for saving power when it's not. Or maybe I am looking at things the wrong way, and I should thank AMD for saving more power in C3 than Intel does? -- Jean Delvare ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: CONFIG_SUSPEND and power consumption 2007-08-20 10:11 ` Oliver Neukum 2007-08-20 15:34 ` Jean Delvare @ 2007-08-20 17:29 ` Pavel Machek 2007-08-20 19:08 ` Rafael J. Wysocki 1 sibling, 1 reply; 8+ messages in thread From: Pavel Machek @ 2007-08-20 17:29 UTC (permalink / raw) To: Oliver Neukum; +Cc: Jean Delvare, Rafael J. Wysocki, LKML Hi! > > If I rmmod "ehci-hcd" then the power consumption is back to 69 W. This > > confirms that this is really USB-related. I have to admit that I did > > not expect an external drive to eat that much power from the system, > > especially when not used. I am told that VIA chips are notoriously bad > > at this kind of things. I'll try the same external drive on an Intel > > system later today. > > > > The last mystery remaining is how USB "activity" can cause my CPU to > > heat. I would expect the south bridge to heat, not the CPU. > > USB, or strictly speaking EHCI, OHCI and UHCI, use DMA. To allow > that the cache coherency logic has to be active. Therefore your CPU > cannot go to C3. Therefore it draws more power. The problem we are > facing in USB is that to get great savings, our coverage has to be perfect. > One device that cannot be autosuspended and we lose most savings. Ok.. but CONFIG_USB_SUSPEND should not really have anything to do with CONFIG_SUSPEND (= s2ram). Perhaps it should depend on CONFIG_PM instead? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: CONFIG_SUSPEND and power consumption 2007-08-20 17:29 ` Pavel Machek @ 2007-08-20 19:08 ` Rafael J. Wysocki 2007-08-20 20:19 ` Pavel Machek 0 siblings, 1 reply; 8+ messages in thread From: Rafael J. Wysocki @ 2007-08-20 19:08 UTC (permalink / raw) To: Pavel Machek; +Cc: Oliver Neukum, Jean Delvare, LKML On Monday, 20 August 2007 19:29, Pavel Machek wrote: > Hi! > > > > If I rmmod "ehci-hcd" then the power consumption is back to 69 W. This > > > confirms that this is really USB-related. I have to admit that I did > > > not expect an external drive to eat that much power from the system, > > > especially when not used. I am told that VIA chips are notoriously bad > > > at this kind of things. I'll try the same external drive on an Intel > > > system later today. > > > > > > The last mystery remaining is how USB "activity" can cause my CPU to > > > heat. I would expect the south bridge to heat, not the CPU. > > > > USB, or strictly speaking EHCI, OHCI and UHCI, use DMA. To allow > > that the cache coherency logic has to be active. Therefore your CPU > > cannot go to C3. Therefore it draws more power. The problem we are > > facing in USB is that to get great savings, our coverage has to be perfect. > > One device that cannot be autosuspended and we lose most savings. > > Ok.. but CONFIG_USB_SUSPEND should not really have anything to do with > CONFIG_SUSPEND (= s2ram). Perhaps it should depend on CONFIG_PM > instead? CONFIG_USB_SUSPEND doesn't depend on CONFIG_SUSPEND. Greetings, Rafael ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: CONFIG_SUSPEND and power consumption 2007-08-20 19:08 ` Rafael J. Wysocki @ 2007-08-20 20:19 ` Pavel Machek 2007-08-20 21:48 ` Rafael J. Wysocki 0 siblings, 1 reply; 8+ messages in thread From: Pavel Machek @ 2007-08-20 20:19 UTC (permalink / raw) To: Rafael J. Wysocki; +Cc: Oliver Neukum, Jean Delvare, LKML Hi! > > > > If I rmmod "ehci-hcd" then the power consumption is back to 69 W. This > > > > confirms that this is really USB-related. I have to admit that I did > > > > not expect an external drive to eat that much power from the system, > > > > especially when not used. I am told that VIA chips are notoriously bad > > > > at this kind of things. I'll try the same external drive on an Intel > > > > system later today. > > > > > > > > The last mystery remaining is how USB "activity" can cause my CPU to > > > > heat. I would expect the south bridge to heat, not the CPU. > > > > > > USB, or strictly speaking EHCI, OHCI and UHCI, use DMA. To allow > > > that the cache coherency logic has to be active. Therefore your CPU > > > cannot go to C3. Therefore it draws more power. The problem we are > > > facing in USB is that to get great savings, our coverage has to be perfect. > > > One device that cannot be autosuspended and we lose most savings. > > > > Ok.. but CONFIG_USB_SUSPEND should not really have anything to do with > > CONFIG_SUSPEND (= s2ram). Perhaps it should depend on CONFIG_PM > > instead? > > CONFIG_USB_SUSPEND doesn't depend on CONFIG_SUSPEND. Strange... what is going on here, then? config USB_SUSPEND bool "USB selective suspend/resume and wakeup (EXPERIMENTAL)" depends on USB && PM && EXPERIMENTAL help If you say Y here, you can use driver calls or the sysfs "power/state" file to suspend or resume individual USB peripherals. Also, USB "remote wakeup" signaling is supported, whereby some USB devices (like keyboards and network adapters) can wake up their parent hub. That wakeup cascades up the USB tree, and could wake the system from states like suspend-to-RAM. If you are unsure about this, say N here. config USB_OTG bool depends on USB && EXPERIMENTAL select USB_SUSPEND default n hmmm, it looks like USB_OTG can be selected without CONFIG_PM, but it selects USB_SUSPEND. Is that okay? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: CONFIG_SUSPEND and power consumption 2007-08-20 20:19 ` Pavel Machek @ 2007-08-20 21:48 ` Rafael J. Wysocki 0 siblings, 0 replies; 8+ messages in thread From: Rafael J. Wysocki @ 2007-08-20 21:48 UTC (permalink / raw) To: Pavel Machek; +Cc: Oliver Neukum, Jean Delvare, LKML On Monday, 20 August 2007 22:19, Pavel Machek wrote: > Hi! > > > > > > If I rmmod "ehci-hcd" then the power consumption is back to 69 W. This > > > > > confirms that this is really USB-related. I have to admit that I did > > > > > not expect an external drive to eat that much power from the system, > > > > > especially when not used. I am told that VIA chips are notoriously bad > > > > > at this kind of things. I'll try the same external drive on an Intel > > > > > system later today. > > > > > > > > > > The last mystery remaining is how USB "activity" can cause my CPU to > > > > > heat. I would expect the south bridge to heat, not the CPU. > > > > > > > > USB, or strictly speaking EHCI, OHCI and UHCI, use DMA. To allow > > > > that the cache coherency logic has to be active. Therefore your CPU > > > > cannot go to C3. Therefore it draws more power. The problem we are > > > > facing in USB is that to get great savings, our coverage has to be perfect. > > > > One device that cannot be autosuspended and we lose most savings. > > > > > > Ok.. but CONFIG_USB_SUSPEND should not really have anything to do with > > > CONFIG_SUSPEND (= s2ram). Perhaps it should depend on CONFIG_PM > > > instead? > > > > CONFIG_USB_SUSPEND doesn't depend on CONFIG_SUSPEND. > > Strange... what is going on here, then? > > config USB_SUSPEND > bool "USB selective suspend/resume and wakeup (EXPERIMENTAL)" > depends on USB && PM && EXPERIMENTAL > help > If you say Y here, you can use driver calls or the sysfs > "power/state" file to suspend or resume individual USB > peripherals. > > Also, USB "remote wakeup" signaling is supported, whereby > some > USB devices (like keyboards and network adapters) can wake > up > their parent hub. That wakeup cascades up the USB tree, and > could wake the system from states like suspend-to-RAM. > > If you are unsure about this, say N here. > > config USB_OTG > bool > depends on USB && EXPERIMENTAL > select USB_SUSPEND > default n > > hmmm, it looks like USB_OTG can be selected without CONFIG_PM, but it > selects USB_SUSPEND. Is that okay? Well, I don't think so. It should depend on the same things as USB_SUSPEND, IMO. Greetings, Rafael ^ permalink raw reply [flat|nested] 8+ messages in thread
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[not found] <20070819153259.2c96b904@hyperion.delvare>
2007-08-19 20:42 ` CONFIG_SUSPEND and power consumption Rafael J. Wysocki
2007-08-20 10:02 ` Jean Delvare
2007-08-20 10:11 ` Oliver Neukum
2007-08-20 15:34 ` Jean Delvare
2007-08-20 17:29 ` Pavel Machek
2007-08-20 19:08 ` Rafael J. Wysocki
2007-08-20 20:19 ` Pavel Machek
2007-08-20 21:48 ` Rafael J. Wysocki
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