My machine specs:
iMac (Retina 5K, 27-inch, 2017)
Processor: 3.4 GHz Quad-Core Intel Core i5
Memory: 16 GB 2400 MHz DDR4
Graphics: Radeon Pro 570 4 GB
Very recently I have started noticing that all cores suddenly report idle for a moment and then go back to full use. Quite similar to garbage collection in a JVM. Please see the attached CPU History picture below. Note how at one place all cores were being fully used but they suddenly black out:
This is a recent phenomenon on my machine. Can someone confirm that it happens on their machine too?
If not, would someone help me identify the cause behind it.
Best Answer
We see that CPU usage pattern all the time. I wouldn’t worry since that’s what cores should do.
I would focus on one specific app at a time in Instruments if you feel it’s not idling when it should be idle and busy when it should be busy.
Missing metrics from time to time isn’t something that concerns me in general absent other much more telling issues like crashes or stalls. Again, in that case I look at what’s stalling and what’s crashing and not the overall CPU graph to identify what next.
In the context of needing a hardware swap or repair, this is very likely software and if the CPU were having issues, you would have thousands of crashes and issues - not that one graph has missed updates. But, I would absolutely open a case with Apple 2 to 4 weeks before warranty ends to have them run diagnostics of offer you to bring in in for a formal hardware diagnostic. MRI would only show something massively wrong, and you clearly don’t have that, so the only way to test this would be in the shop Apple custom diagnostics that they have, plus getting an experienced tech to load test your Mac.