Re: Make CPU use the C2 state
On Mon, Jan 13, 2014 at 9:20 AM, Philip Guenther guent...@gmail.com wrote: C0 is the only state where the CPU does real work; the higher C-states only make sense for when the CPU is idle, so your question presumably is does the CPU get put into a higher C-state when idle. Well, 5.4-current uses the MWAIT instruction for the idle loop when available, which uses the C1 state by default. Have people found 5.4-current to use less power/run cooler since the MWAIT change in early October? The MWAIT instruction can put the CPU into a higher C-state if the CPU supports it, but we don't use or expose that yet. I have no interest in adding Yet Another Knob, but maybe making the decision based off the existing hw.setperf sysctl would be reasonable and sufficient, overloading the range to not just change the speed but also use a deeper C-state hw.setperf is smaller, ala C3 - 0-33 C2 - 34-65 C1 - 66-100 Or maybe that's a bad idea. Thanks for the explanation, it was very informative. This would most likely solve my problem. But as other people have said it probably should be a separate sysctl if implemented. John
Re: Make CPU use the C2 state
But as other people have said it probably should be a separate sysctl if implemented. I completely doubt that. We've encountered this before on other processor families, and always chosen to dumb down all the speed/power knobs to 1 user controllable knob.
Re: Make CPU use the C2 state
On Mon, Jan 13, 2014 at 12:20:27AM -0800, Philip Guenther wrote: On Sun, Jan 12, 2014 at 11:16 PM, John Rogers microspar...@gmail.com wrote: I'm not an expert on this but my theory is that the problem is not that the CPU is running too fast but rather that it is running in a high power state, presumably C0. Do you know if apmd adjusts the c-state? C0 is the only state where the CPU does real work; the higher C-states only make sense for when the CPU is idle, so your question presumably is does the CPU get put into a higher C-state when idle. Well, 5.4-current uses the MWAIT instruction for the idle loop when available, which uses the C1 state by default. Have people found 5.4-current to use less power/run cooler since the MWAIT change in early October? The MWAIT instruction can put the CPU into a higher C-state if the CPU supports it, but we don't use or expose that yet. I have no interest in adding Yet Another Knob, but maybe making the decision based off the existing hw.setperf sysctl would be reasonable and sufficient, overloading the range to not just change the speed but also use a deeper C-state hw.setperf is smaller, ala C3 - 0-33 C2 - 34-65 C1 - 66-100 Or maybe that's a bad idea. The problem is C-states slows down additional components, not just the CPU speed. Some users only want to change the CPU speed and others want to increase the battery life of their laptops even if the laptop runs slightly slower. Inevitably, you will need add also a new sysctl entry to enable/disable the c-states, something like hw.setperf.c-states. -- Juan Francisco Cantero Hurtado http://juanfra.info
Re: Make CPU use the C2 state
On Thu, Jan 16, 2014 at 04:20, Juan Francisco Cantero Hurtado wrote: CPU speed. Some users only want to change the CPU speed and others want to increase the battery life of their laptops even if the laptop runs slightly slower. Inevitably, you will need add also a new sysctl entry heh, well, it is inevitable that some users will *want* a new sysctl, but whether we need to provide it is a separate matter. :)
Re: Make CPU use the C2 state
On Sun, Jan 12, 2014 at 11:16 PM, John Rogers microspar...@gmail.com wrote: I'm not an expert on this but my theory is that the problem is not that the CPU is running too fast but rather that it is running in a high power state, presumably C0. Do you know if apmd adjusts the c-state? C0 is the only state where the CPU does real work; the higher C-states only make sense for when the CPU is idle, so your question presumably is does the CPU get put into a higher C-state when idle. Well, 5.4-current uses the MWAIT instruction for the idle loop when available, which uses the C1 state by default. Have people found 5.4-current to use less power/run cooler since the MWAIT change in early October? The MWAIT instruction can put the CPU into a higher C-state if the CPU supports it, but we don't use or expose that yet. I have no interest in adding Yet Another Knob, but maybe making the decision based off the existing hw.setperf sysctl would be reasonable and sufficient, overloading the range to not just change the speed but also use a deeper C-state hw.setperf is smaller, ala C3 - 0-33 C2 - 34-65 C1 - 66-100 Or maybe that's a bad idea. Philip Guenther
Make CPU use the C2 state
Hi. I have installed OpenBSD 5.4 on a laptop. So far everything runs fine but I have the problem that it runs fairly hot even in idle. I used to run FreeBSD on it before and it behaved very similar then, until I read [1]. Setting performance_cx_lowest=C2 and economy_cx_lowest=C2 did wonder to this machine and effectively lowered the temperature and fan speed to acceptable levels. My understanding is that this uses ACPI to make the processor run in at least C2 state which makes it wake up somewhat slower but in general decreases power usage. My question is if I can do something similar with OpenBSD. I've read through the source code to acpicpu(4) [2] and it mentions c-states here and there, but I'm not used to the OpenBSD kernel source code and is unable to tell how I can utilize it. John [1] https://wiki.freebsd.org/TuningPowerConsumption [2] http://www.openbsd.org/cgi-bin/cvsweb/src/sys/dev/acpi/acpicpu.c?rev=HEAD
Re: Make CPU use the C2 state
On Sun, Jan 12, 2014 at 05:29:02PM +0100, John Rogers wrote: Hi. I have installed OpenBSD 5.4 on a laptop. So far everything runs fine but I have the problem that it runs fairly hot even in idle. I used to run FreeBSD on it before and it behaved very similar then, until I read [1]. Setting performance_cx_lowest=C2 and economy_cx_lowest=C2 did wonder to this machine and effectively lowered the temperature and fan speed to acceptable levels. My understanding is that this uses ACPI to make the processor run in at least C2 state which makes it wake up somewhat slower but in general decreases power usage. My question is if I can do something similar with OpenBSD. I've read through the source code to acpicpu(4) [2] and it mentions c-states here and there, but I'm not used to the OpenBSD kernel source code and is unable to tell how I can utilize it. John [1] https://wiki.freebsd.org/TuningPowerConsumption [2] http://www.openbsd.org/cgi-bin/cvsweb/src/sys/dev/acpi/acpicpu.c?rev=HEAD Try apmd(8). -- Juan Francisco Cantero Hurtado http://juanfra.info
Re: Make CPU use the C2 state
On Mon, Jan 13, 2014 at 4:10 AM, Juan Francisco Cantero Hurtado i...@juanfra.info wrote: On Sun, Jan 12, 2014 at 05:29:02PM +0100, John Rogers wrote: Hi. I have installed OpenBSD 5.4 on a laptop. So far everything runs fine but I have the problem that it runs fairly hot even in idle. I used to run FreeBSD on it before and it behaved very similar then, until I read [1]. Setting performance_cx_lowest=C2 and economy_cx_lowest=C2 did wonder to this machine and effectively lowered the temperature and fan speed to acceptable levels. My understanding is that this uses ACPI to make the processor run in at least C2 state which makes it wake up somewhat slower but in general decreases power usage. My question is if I can do something similar with OpenBSD. I've read through the source code to acpicpu(4) [2] and it mentions c-states here and there, but I'm not used to the OpenBSD kernel source code and is unable to tell how I can utilize it. John [1] https://wiki.freebsd.org/TuningPowerConsumption [2] http://www.openbsd.org/cgi-bin/cvsweb/src/sys/dev/acpi/acpicpu.c?rev=HEAD Try apmd(8). Thanks for the suggestion. I have added apmd_flags=-C to /etc/rc.conf.local. It looks like it has some effect on the machine but it is still running at much higher temperature in idle compared to what is normal for it. I'm not an expert on this but my theory is that the problem is not that the CPU is running too fast but rather that it is running in a high power state, presumably C0. Do you know if apmd adjusts the c-state? John
