Single core always close to 100% load on Ubuntu 16.04 (without any work being done)
My Ubuntu 16.04 machine has 4 CPU cores, and one of them (which one exactly varies) always has a load of 90% to 100%.
This is true no matter what I'm doing, and even when I'm not doing anything at all, with no window open. It's happening right after boot or hours into work.
I've read the two popular related questions here and here, but these didn't help, unfortunately.
During the major part of my working time, my productivity is not affected by this problem. The only reasons I know about the problem then is that the fans are always working at their maximum power and Ubuntu's system monitoring says that one of the cores is under heavy load.
But perhaps 10% of my working time is affected by incredibly bad responsiveness, as an additional manifestation.
Especially the UI (during animations and when reacting to clicks) is super slow. That lead me to the idea that, perhaps, the CPU is doing the GPU's work as well. But that was probably an unfounded belief only, and the data below seems to contradict as well.
My concern is whether this problem, if I can't fix it, will have a (significant) impact on my computer's lifetime or not. I don't know what a constant load of >90% does to a CPU over months or years.
Anyway, here's the data that I could collect from my machine, which may be related or helpful:
top:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
415 root 20 0 0 0 0 R 97,3 0,0 1:39.30 kworker/2:2
2442 john 20 0 663828 38704 29852 S 3,3 0,5 0:00.90 gnome-terminal-
1194 root 20 0 335728 69900 48392 S 2,3 0,9 0:08.36 Xorg
1821 john 20 0 1423440 114660 77600 S 1,3 1,5 0:03.77 compiz
6 root 20 0 0 0 0 D 0,3 0,0 0:00.84 kworker/u8:0
grep . -r /sys/firmware/acpi/interrupts/:
/sys/firmware/acpi/interrupts/sci: 36
/sys/firmware/acpi/interrupts/error: 0
/sys/firmware/acpi/interrupts/gpe00: 0 invalid
/sys/firmware/acpi/interrupts/gpe01: 0 invalid
/sys/firmware/acpi/interrupts/gpe02: 0 invalid
/sys/firmware/acpi/interrupts/gpe03: 36 enabled
/sys/firmware/acpi/interrupts/gpe04: 0 invalid
(...)
/sys/firmware/acpi/interrupts/gpe1F: 0 disabled
/sys/firmware/acpi/interrupts/sci_not: 0
/sys/firmware/acpi/interrupts/ff_pmtimer: 0 invalid
/sys/firmware/acpi/interrupts/ff_rt_clk: 0 disabled
/sys/firmware/acpi/interrupts/gpe_all: 36
/sys/firmware/acpi/interrupts/ff_gbl_lock: 0 enabled
/sys/firmware/acpi/interrupts/ff_pwr_btn: 0 enabled
/sys/firmware/acpi/interrupts/ff_slp_btn: 0 invalid
uname -a:
Linux my-host-name 4.4.0-47-generic #68-Ubuntu SMP Wed Oct 26 19:39:52 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
cat /proc/cmdline:
BOOT_IMAGE=/vmlinuz-4.8.0-28-generic.efi.signed root=/dev/mapper/ubuntu--vg-root ro quiet splash vt.handoff=7
lspci -v:
00:00.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1576
Subsystem: Hewlett-Packard Company Device 81f9
Flags: bus master, fast devsel, latency 0
00:00.2 IOMMU: Advanced Micro Devices, Inc. [AMD] Device 1577
Subsystem: Hewlett-Packard Company Device 81f9
Flags: bus master, fast devsel, latency 0, IRQ 24
Capabilities: <access denied>
00:01.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Carrizo (rev ca) (prog-if 00 [VGA controller])
DeviceName: ATI EG BROADWAY
Subsystem: Hewlett-Packard Company Carrizo
Flags: bus master, fast devsel, latency 0, IRQ 227
Memory at e0000000 (64-bit, prefetchable) [size=256M]
Memory at f0800000 (64-bit, prefetchable) [size=8M]
I/O ports at 4000 [size=256]
Memory at f0500000 (32-bit, non-prefetchable) [size=256K]
Expansion ROM at f0580000 [disabled] [size=128K]
Capabilities: <access denied>
Kernel driver in use: amdgpu
Kernel modules: amdgpu
...
00:08.0 Encryption controller: Advanced Micro Devices, Inc. [AMD] Device 1578
Subsystem: Hewlett-Packard Company Device 81f9
Flags: bus master, fast devsel, latency 0, IRQ 255
Memory at f0540000 (64-bit, prefetchable) [size=128K]
Memory at f0300000 (32-bit, non-prefetchable) [size=1M]
Memory at f0570000 (32-bit, non-prefetchable) [size=4K]
Memory at f056a000 (32-bit, non-prefetchable) [size=8K]
Capabilities: <access denied>
...
01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller (rev 07)
Subsystem: Hewlett-Packard Company RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller
Flags: bus master, fast devsel, latency 0, IRQ 225
I/O ports at 3000 [size=256]
Memory at f0400000 (64-bit, non-prefetchable) [size=4K]
Memory at f0100000 (64-bit, prefetchable) [size=16K]
Capabilities: <access denied>
Kernel driver in use: r8169
Kernel modules: r8169
02:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8723BE PCIe Wireless Network Adapter
DeviceName: Sanji2
Subsystem: Hewlett-Packard Company RTL8723BE PCIe Wireless Network Adapter
Flags: bus master, fast devsel, latency 0, IRQ 231
I/O ports at 2000 [size=256]
Memory at f1000000 (64-bit, non-prefetchable) [size=16K]
Capabilities: <access denied>
Kernel driver in use: rtl8723be
Kernel modules: rtl8723be
Can anybody help?
I've been able to track down the precise cause of this problem, although that's not really a solution to the problem:
Doing a fresh re-install, changing settings one-by-one and installing packages one-by-one, it turned out that I could consistently re-produce (and even "toggle") the problem by setting "Built-in Display" to "Off" in the system settings.
I had an external monitor connected via HDMI, and in order to save power, I wanted to turn off the built-in display completely (which worked but caused high CPU load and slowed-down UI) instead of just mirroring it (which worked without any downsides).
In addition to the problem of high CPU load, there was a continuous, high-pitched but quiet, cheeping sound coming from the computer (laptop) when "Built-in Display" was turned off.