CPU usage when PC is idle

Scottyboy99 · 12 Dec 2015

This is not an issue but more a curiosity. I have the old Windows cup / ram monitor running as a gadget on Windows 10. When the PC is idle for a few minutes I notice the cup usage always spikes to around 10-13% and stays around that mark. As soon as I touch mouse and move it it then plummets to 0 or 1%. Is this normal? I wonder what it could be doing. It's not as if I can use task manager to see because as soon as I move the mouse or go to use the PC the usage returns to 0 or 1? I presume Windows is doing housekeeping stuff and it's a non issue?

cheers, Wayne

Scottyboy99 · 12 Dec 2015

Ok, I left task manager open and waited for a few mins in front of computer not touching anything. The service that starts up is system and compressed memory. It's always about 13% and seems constant when machine isn't in use. Like I say, as soon as I touch the mouse and move it the service reduces to 0. The actual memory amount this service consumes is only about 50 mb.

UPDATE - so I left it idle quite a while, about 20-25 minutes. Long enough for my screensaver to kick in. Of course when I touched the mouse to resume desktop cpu usage was at 0. What was interesting is I looked at c: drive (SSD) which had consistently been 247 Gb free but it had risen to 252 gb. And when I left the machine idle again for about ten mins the cpu usage stayed at 0. So maybe whatever the system was doing got enough idle time to finish. It'll be interesting to see after shutdown tonight whether this cpu usage rises again when I switch on again tomorrow - am hoping not. I guess it's similar to what I saw on Windows 7 (still faithfully on my older laptop) where I would notice the available free space, on occasions, fluctuate (mainly rising) after a decent amount of idle time. I'm not one to leave my machine on for prolonged periods when not using it and as the Windows 10 desktop is newish and I'm almost always doing stuff/installing stuff at the moment to bring it to similar functionality to my other laptop (mainly games) it gets very little idle time for more than a few minutes at most. So I wonder if this process also has something to do with disk space clean up too. For what it's worth fast startup is enabled on my machine (it was on by default - boy is startup fast!), I doubt it's relevant to this but maybe worth mentioning .

Snakeyes · 13 Dec 2015

Might be swap file adjustments that are causing the change in your SSD storage. Try setting max and min for swap file at the same size and this fluctuation should disappear. The system and compressed memory is generally always active and its level of percentage CPU and memory usage is possibly linked to your CPU speed and physically installed memory.

dalchina · 13 Dec 2015

Hi, you might like to have a look at this thread:
Solved Is this normal? System and compressed memory process ALWAYS at 20% cpu - Windows 10 Forums

Scottyboy99 · 13 Dec 2015

I rebooted earlier and the cpu usage did not spike to 13% after leaving alone for about twenty mins so I guess whatever that service needed to do was finally given time to finish. I'll be keeping an eye on this but it seems all is well

M A Weiss · 25 Oct 2019

I notice that when my monitor goes on standby for a while, CPU usage gets full of spikes. I see this when I wake the system and see the recent history graphs on Task Manager.
If Windows is allowed to run for 30 days without reboot, this activity will increase to the point where the monitor with blink on and off every 2 seconds. When I start using the machine, the spikes cease and the graphs go to a pretty flat line.
I can't tell what process is causing this because it stops as soon as I wake the display.
It's been an open question of mine since March when I first noticed it.
Is there a way to tell what application or process was using high CPU AFTER you wake the machine?

dalchina · 26 Oct 2019

Hi please see this for at least two unrelated approaches:
windows - Tracking CPU and Memory usage per process - Stack Overflow

M A Weiss · 26 Oct 2019

How do you know what to track when you don't know which process was active while the monitor was asleep? I've tried playing with Resource Monitor, but kernel time doesn't tell me much other than total load.

dalchina · 26 Oct 2019

windows - Log %CPU by Process over time - Super User