[Vm-dev] [OpenSmalltalk/opensmalltalk-vm] [Win10] [Squeak] High CPU usage in different images for a few minutes after resume from sleep (#537)

Christoph Thiede notifications at github.com
Sun Nov 22 14:33:54 UTC 2020

I noticed this a few times, and today I observed it a bit: After resuming my Win10 message from sleep, my two open Squeak.exe processes both made up each ~14% CPU load. I suspect this performance gap is caused by the VM because, in one image, a nearly empty Morphic world was open (two non-stepping windows only) and in the other one, a completely empty MVC world; both images were responsive; and according to Squeak's CPU watcher, only ~20% of time were spent in the UI process but 80% in idle. After a few minutes, both VM instances fall back to ~0.1% of total CPU usage.

Is there any chance to find an explanation for this behavior in the VM implementation, are there any hidden background operations (maybe certain WM_MESSAGES) that are triggered after resuming from sleep? Does anyone else notice similar behavior?

For sake of completeness, I should mention that my RAM and disk usage are chronically near maximum (90% of RAM in use, 25 GB on SSD free. Squeak images are so large 😐). But this does not change after a few minutes so I don't think it explains the observed slowdown completely.

VM build 202010232046; but I could already have experienced similar issues a few months ago.

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