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Linux Thermal Daemon Monitors and Controls Temperature in Tablets, Laptops

Intel’s Open Source Technology Center has released an open source tool to monitor and control temperature in tablets, ultrabooks and laptops. The Linux Thermal Daemon can use the latest thermal drivers in the Linux kernel, not just the standard cpufreq subsystem, to provide CPU temperature control.  

Due to constrained system size, small form factor devices reach their maximum temperature with relatively less load than desktops and servers. And as they get smaller and thinner, traditional cooling methods such as heat sinks and fans are being designed out of the devices. Developers can’t rely only on hardware and BIOS to regulate temperature without negatively impacting performance. 

Thermal Daemon “proactively tries to limit the temperature so BIOS doesn’t take a drastic action to cool the system,” said Srinivas Pandruvada, the Thermal Daemon project lead in the Open Source Technology Center at Intel. “The hardware and BIOS can (regulate) itself but it’s usually not an optimal solution, depending on their implementation. And, if the temperature reaches critical point, it can Thermal Daemon diagramresult in powering down of the system. ”

Tapping Intel Drivers for Temperature Control

The Linux kernel already holds a number of power management drivers that regulate temperature and cooling in various ways and rely  on ACPI configuration to use them. But there are new cooling drivers developed by Intel, for which the device must first ask the driver to take action. The Thermal Daemon tool manages cooling drivers, either through preconfigured or custom settings.

“Developers can access XML configuration files and specify what level of temperature and what cooling drivers they want to use,” Pandruvada said. “But for most developers, the default settings and cooling actions should be enough.”

By tapping into the latest kernel drivers such as Intel P-State , RAPL (running average power limit) and PowerClamp, Thermal Daemon allows developers to more precisely control the temperature set point for a given use case.

However, not all of the above drivers are accessible to all hardware. The Intel P-state drivers are specific to the new generation Sandy Bridge and Ivy Bridge processors, for example.

“If the latest drivers are not available, then the daemon will revert to x86 model specific registers and the Linux ‘cpufreq subsystem’ to control system cooling,” according to the Intel news release.

Download and Get Involved

This is the first code release since the Thermal Daemon project kicked off in December, so the driver hasn’t been incorporated yet into any distributions. Intel is actively looking for feedback and features for consideration in future versions, Pandruvada said.

Thermal Daemon can also be applied to other computing form factors such as mobile and server, but is being targeted initially towards the tablet and laptop segments.

Download the Thermal Daemon source code and documentation from the Open Source Technology Center at https://01.org/linux-thermal-daemon

 

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  • Evert Vorster Said:

    Hi there. I have a Intel i7 in a laptop, running linux. My problem with the p-states driver is that even on the "powersave" governor, it's always running the cpu flat out, and thus the fan is quite noisy and temps are high, even with days of a loadavg 0. Surely this can't be right? Is powersave not supposed to switch off cores and clock down the frequency of the remaining ones if there is no load to save on power, as the name would suggest? I had a quick play with the termal daemon software linked to above, but that, also did not bring down the temperatures on my laptop. So, I just have a bash script that runs now, and checks loadavg, then sets cpu frequencies manually down if nothing much is happening, but surely the p-states driver should be capable of much more than just frequency adjustments? Also, it should clock down automatically on powersave, unless there is some part of the puzzle that I am missing?

  • Curtis Said:

    It does sound like something is awry in your system. It should be able to keep your processor in a pretty cool state, and ramp up/down the processor to fit the needs of the machine at any given moment. Since your machine is getting extremely hot, I would venture to guess that this might tell you what you already know. But it might be worth installing i7z or checking powertop to ensure that your processor is reaching the C-states (sleep states). From the bit of info above, you might find that it is not. If it is not, then you should revert back to the old acpi-cpufreq module and ondemand driver. This can be done from the kernel command line. The intel_pstate driver is typically built into the kernel so that is really the only way to revert back. The intel_pstate driver is new software, and like all new software, it is bound to have bugs. In most cases it seems to work quite well. But you re not the first person I have heard of who has had this problem. Still, the pstate driver continues to enjoy development, so hopefully any issues will be ironed out in quick order. Add 'intel_pstate=disable' to the kernel command line if you cannot figure things out otherwise. The ondemand driver has apparently seen some great improvments on 3.12, so that will probably fit your needs until things are worked out.

  • Arup Said:

    The pstate doesn't clock down the frequency and it has been found out that running lower clock doesn't save power. Rather it depends on a function called 'race to halt' as defined here https://plus.google.com/117091380454742934025/posts/2vEekAsG2QT

  • visnotjl Said:

    I have been using thermal daemon on an HP DV 6000. Pretty good results. The most appreciable effect is tghe lowering of the temperature of the nvidia graphic adapter. (From average 73 C to 45 C). I couldn't know details of the process. Anyway the result il very good.

  • mohammed Said:

    i am new to linux and i want to know what the temperature of my laptop is can you help me


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