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sgsdxzy
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Joined: 22 May 2012
Posts: 24
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 Posted: Thu Jul 04, 2013 7:47 am Post subject: Intel_pstate: One Core always 100% C0 state |
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I am using a laptop with Intel Ivy bridge core i7 3610QM. I updated my kernel to 3.10 and started to use intel_pstate as scaling driver:
#cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
intel_pstate
However I find that one of my four cores is always in C0 state even when there is no activities. I monitored it using i7z:
Core [core-id] :Actual Freq (Mult.) C0% Halt(C1)% C3 % C6 % C7 % Temp
Core 1 [0]: 3288.24 (32.97x) 99.7 0 0 0 0 83
Core 2 [1]: 3138.62 (31.47x) 1 0 0 0 99.7 74
Core 3 [2]: 3175.46 (31.84x) 1 0.891 0 0 99 76
Core 4 [3]: 3177.34 (31.86x) 1 0.21 0 0 99.3 71
Also cpu frequencies never scale down, resulting in very high temp.
#cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
powersave
It does say powersave, and my cpu is capable of 1.20Ghz to 3.30Ghz
I don't know if I misconfigured or misunderstood something. Can someone tell me why?
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eccerr0r
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Joined: 01 Jul 2004
Posts: 9677
Location: almost Mile High in the USA
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| Posted: Thu Jul 04, 2013 5:52 pm Post subject: |
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Are you sure you're running nothing? Get out of X completely, etc.
My i7-2700K and i5-3317U do stay out of C0 state on all cores when completely idle... If you have some quick interrupt handler that doesn't take that much cpu, it could trigger it to stay in C0...
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Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
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sysrqalt
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Joined: 02 Jul 2013
Posts: 1
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| Posted: Fri Jul 05, 2013 4:24 am Post subject: |
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| Switching Full dynticks system to Idle dynticks system under Timers subsystem in my kernel config fixed both problems for me. |
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sgsdxzy
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Joined: 22 May 2012
Posts: 24
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| Posted: Fri Jul 05, 2013 5:25 am Post subject: |
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| eccerr0r wrote: | Are you sure you're running nothing? Get out of X completely, etc.
My i7-2700K and i5-3317U do stay out of C0 state on all cores when completely idle... If you have some quick interrupt handler that doesn't take that much cpu, it could trigger it to stay in C0... |
Yeah, I truned off X and get the same result... |
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sgsdxzy
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Joined: 22 May 2012
Posts: 24
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| Posted: Fri Jul 05, 2013 5:25 am Post subject: |
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| sysrqalt wrote: | | Switching Full dynticks system to Idle dynticks system under Timers subsystem in my kernel config fixed both problems for me. |
Thanks, I am using full dynticks too. I will try idle dynticks.
Last edited by sgsdxzy on Fri Jul 05, 2013 5:52 am; edited 1 time in total |
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sgsdxzy
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Joined: 22 May 2012
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| Posted: Fri Jul 05, 2013 5:41 am Post subject: |
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| Switching to Idle dynticks system does fix the problem. But I am still wondering if it was a bug.... |
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eccerr0r
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Joined: 01 Jul 2004
Posts: 9677
Location: almost Mile High in the USA
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| Posted: Fri Jul 05, 2013 6:29 pm Post subject: |
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No, it's not a bug. That's an interrupt handler and if it keeps on pinging the machine, it can't stay in sleep.
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Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
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sgsdxzy
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Joined: 22 May 2012
Posts: 24
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| Posted: Sat Jul 06, 2013 4:52 am Post subject: |
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| eccerr0r wrote: | | No, it's not a bug. That's an interrupt handler and if it keeps on pinging the machine, it can't stay in sleep. |
I am just wondering if it is taking too much cpu resources, resulting in too high temp, and while full dynticks is designed to save power, using too much energy... |
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kernelOfTruth
Watchman
Joined: 20 Dec 2005
Posts: 6111
Location: Vienna, Austria; Germany; hello world :)
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| Posted: Sat Jul 06, 2013 3:38 pm Post subject: |
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| sgsdxzy wrote: | | eccerr0r wrote: | | No, it's not a bug. That's an interrupt handler and if it keeps on pinging the machine, it can't stay in sleep. |
I am just wondering if it is taking too much cpu resources, resulting in too high temp, and while full dynticks is designed to save power, using too much energy... |
full dynticks in fact does currently eat more energy
I've experienced this first-hand on my laptop where e.g. battery runtime with full dynticks (around 2.5 - 3 hours) went up to 8-9 hours with idle dynticks
it's far from ready to suit its destined purpose yet ...
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