I'm a happy owner of the Dell XPS 9570 laptop with Ubuntu 18.04 LTS installed (kernel 4.15.0-46, nouveau driver) and external keyboard + monitor. It works really well, and its battery life is also great… well, at least until wake up from suspend (deep sleep). Always after waking up, Ubuntu drains my battery very fast, and fans work louder than usual. Closing all running apps doesn't make any difference :/
It cannot be related to the hardware, because Windows 10 pre-installed on this laptop does not have such problem.
I've checked output of the dmesg
, top
, powertop
commands and I haven't found anything unusual. CPU usage is very low. Also I've tried the Nvidia proprietary driver, but didn't help. Any tips what may be wrong?
Best Answer
Short answer: It turned out to be a problem somewhere between kernel 4.15 and the touchpad.
Disabling the touchpad solved the problem:
This is an acceptable workaround for me, since most of the time I use an external mouse. In rare cases, when I don't have a mouse at hand, I solve the problem by disabling + enabling the touchpad after waking up:
EDIT March 2020: Some time ago, I've realized that a moment of using the touchpad, after resuming the laptop also solves the problem.
Long answer
The
top
command showed a low overall CPU usage (below 8%), but surprisingly the following command:revealed that all CPU cores were running at the highest frequency (~3.8 GHz)!, while I was expecting to see the lowest possible frequency (0.8 GHz) due to the idle state. The
sudo powertop
has proven that the high power consumption indeed was coming from the CPU.So I came back to the results of the
top
command, watched it closely, and one process looked suspicious: irq/51-SYNA2393:The
dmesg | grep SYNA
output:revealed that IRQ 51 comes from the laptop touchpad. That's how I found the culprit.
To be honest, I'm not sure it it's a bug inside Linux kernel, or simply my touchpad is not top-notch supported. When I'll try a newer Ubuntu version with newer kernel I'll update this post.