0

I'm running Windows 8.1 on my laptop, and it is set to do nothing when the lid is closed.

However, I often notice that the fan gets very loud, and when I open the laptop I can see CPU usage suddenly drop from 70% to almost nothing. It seems that System process is using 30%+ CPU while the lid is closed, and then suddenly stops when I open it. What could cause this behavior?

Improve this question
1
  • any update? can you confirm this or do you need help looking at the ETL?
    – magicandre1981
    Aug 6, 2016 at 7:38

1 Answer 1

Reset to default
1

To capture a trace of the CPU usage. Install the WPT from Win10 SDK, open a cmd.exe as admin and run this command:

xperf -on latency -stackwalk profile -buffersize 2048 -MaxFile 1024 -FileMode Circular && timeout -1 && xperf -d C:\highCPUUsage.etl

Now do the action that triggers the CPU usage of the system process. When you see the issue, wait 30s, open the lid, go to the cmd.exe and press a key to stop logging.

My guess is that during analyzing the ETL file with WPA it will show, that the CPU usage comes from ntoskrnl.exe!MiScrubMemoryWorker and you'll see something like this:

Line #, DPC/ISR, Process, Stack Tag, Stack, Count, TimeStamp (s), % Weight
8, , , ,    |    |    |- ntoskrnl.exe!MiScrubMemoryWorker, 79667, , 12,45
9, , , ,    |    |    |    ntoskrnl.exe!MiScrubNode, 79667, , 12,45
10, , , ,   |    |    |    ntoskrnl.exe!MiScrubNodeLargePages, 79667, , 12,45
11, , , ,   |    |    |    ntoskrnl.exe!MiScrubNodeLargePageList, 79667, , 12,45
12, , , ,   |    |    |    |- ntoskrnl.exe!MiScrubPage, 79663, , 12,45
13, , , ,   |    |    |    |    |- ntoskrnl.exe!RtlScrubMemory, 79653, , 12,45
14, , , ,   |    |    |    |    |    |- ntoskrnl.exe!RtlpGenericRandomPatternWorker, 38549, , 6,02

This is a function to test the memory for errors by filling / reading some patterns (ntoskrnl.exe!RtlpGenericRandomPatternWorker).

This is by design and happens when the idle maintenance task kicks up when your device is idle.

To stop it, use Task Scheduler and disable the idle maintenance task.

Improve this answer
2
  • Thanks, I'll try it next time I'm on my laptop. So you reckon its just testing memory while idle?
    – riv
    Jun 20, 2016 at 13:34
  • I've asked this Microsoft when I saw it the first time so I now know what the function does.
    – magicandre1981
    Jun 20, 2016 at 14:45

Not the answer you're looking for? Browse other questions tagged .