Created attachment 115054 [details] dmesg of running system Hardware: Retina MacBook Pro 13", Intel Core i5 4258U with Intel Iris 5100 integrated graphics. Distribution: Ubuntu 15.04 daily release Kernel version: 3.19.0-13-generic Output from glxgears -info: GL_RENDERER = Mesa DRI Intel(R) Haswell GL_VERSION = 3.0 Mesa 10.5.2 GL_VENDOR = Intel Open Source Technology Center This bug affects all distributions using kernels after 3.14. On my hardware, 1 core of 4 is stuck at about 70% load, even without any CPU-intensive operation running. If the system is booted without loading i915 module the CPU load stays at normal levels.
Use "sudo perf top" to see what is hogging the CPU.
perf top reveals that: acpi_ns_search_one_scope acpi_os_read_port acpi_os_write_port are eating about 15% of CPU each. If the system is loaded with "i915.modeset=0" CPU levels are normal and perf does not reveal any strange activity.
Intriguing, let's see the callchain to see what it triggering the ACPI activity. So can you please 'perf record -g -a sleep 60; perf report | head -500' and attach the output.
Created attachment 115069 [details] perf output
After some heavy googling, this[1] workaround seem to work. I've attached the perf output anyway, this situation needs to be addressed. Cheers. [1]: http://askubuntu.com/questions/176565/why-does-kworker-cpu-usage-get-so-high
So which GPE was it?
GPE 66.
Please try kernel v4.4.
No response in months, closing. Please reopen if the problem persists with latest kernels.
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