Not sure the status of this bug, but I just installed Ubuntu
5.4.0-6ubuntu1~16.04.2 with Linux version 4.4.0-38-generic on a dual
core machine with an onboard GeForce 9400.
I ran into the issue of one of the cores running at 100% when ever I
turned on my monitor and connected to the terminal via DVI/HDMI. If I
reboot and only ssh to the machine I get <1% usage across both cores at
idle, but as soon as I switch on the monitor one of the cores jumps to
100%
I ran "sudo perf record -g -a sleep 20" then "sudo perf report --sort
comm,dso" and this is what I found in the report:
- 100.00% 99.85% kworker/1:7 [kernel.kallsyms]
- 100.00% ret_from_fork
kthread
worker_thread
- process_one_work
- 99.97% nvif_notify_work
+ nouveau_connector_hotplug
+ 0.03% nvkm_notify_work
+ 0.00% vmstat_update
0.00% native_write_msr_safe
- 100.00% 0.09% kworker/1:7 [nouveau]
- 99.88% nvif_notify_work
- nouveau_connector_hotplug
- 99.87% drm_helper_hpd_irq_event
- 99.86% nouveau_connector_detect
+ 96.48% drm_get_edid
+ 3.39% i2c_transfer
+ 0.00% drm_mode_object_find
+ 0.00% mutex_unlock
+ 0.01% mutex_lock
+ 0.09% ret_from_fork
+ 0.03% nvkm_notify_work
+ 99.96% 0.00% kworker/1:7 [drm_kms_helper]
+ 99.93% 0.05% kworker/1:7 [i2c_algo_bit]
+ 96.56% 0.01% kworker/1:7 [drm]
+ 0.01% 0.00% kworker/1:7 [forcedeth]
So it looks like I got struck but this same hotplug issue. If I connect
to my monitor via VGA i don't get the CPU spike...works for me since I
am running my machine headless but if anyone else needs to connect via
HDMI/DVI this could be an issue. I'm not sure if installing the nvidia
drivers fixes the hotplug cpu spike up.
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https://bugs.launchpad.net/bugs/1248256
Title:
[MacBookPro10,1] Plugging in displayport monitor causes kworker to
take 100% CPU
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