@Dmitry@Parallels
Lately I've also encountered periods where the guest Windows OS is severely dropping input, but the host OS is registering the input with no problem. This comes and goes periodically throughout the day, even when neither the host nor guest OS is under any load. I finally remembered to gather technical data when this happened just now (Report ID 171544073).
I captured this data immediately after I notice the Windows OS dropping keyboard input when typing into Visual Studio. The problem occurred in Notepad++ as well at the same time. I was able to quickly switch back and forth between the host and guest OSes, and the issue did not happen on the host OS but happened on the guest OS within Parallels. To demonstrate the issue, between 2:40:45pm and 2:40:50pm Boston time (immediately prior to gathering the technical data) I started typing a sentence into Notepad++ and around 50-60% of the keys I typed were not registering. At the time (according to task manager) there was near-zero load on the guest OS, and the load on the host MacOS was around 10-15% (Parallels Desktop was using 9.3% CPU on the host OS).
Thank you, KorkyPlunger, for the detailed issues description! I have reviewed the logs and it's full with the messages:
04-11 14:15:49.144 W /LocalDevices:36812:85007/ [CPs2Mouse] Mouse buffer full (guest hang?)
04-11 14:15:49.147 W /LocalDevices:36812:85007/ [CPs2Mouse] Mouse buffer full (guest hang?)
04-11 14:15:49.148 W /LocalDevices:36812:85007/ [CPs2Mouse] Mouse buffer full (guest hang?)
04-11 14:15:49.150 W /LocalDevices:36812:85007/ [CPs2Mouse] Mouse buffer full (guest hang?)
04-11 14:15:49.152 W /LocalDevices:36812:85007/ [CPs2Mouse] Mouse buffer full (guest hang?)
04-11 14:15:49.154 W /LocalDevices:36812:85007/ [CPs2Mouse] Mouse buffer full (guest hang?)
04-11 14:15:49.156 W /LocalDevices:36812:85007/ [CPs2Mouse] Mouse buffer full (guest hang?)
04-11 14:15:49.158 W /LocalDevices:36812:85007/ [CPs2Mouse] Mouse buffer full (guest hang?)
04-11 14:15:49.160 W /LocalDevices:36812:85007/ [CPs2Mouse] Mouse buffer full (guest hang?)
When it happens once again, please send us a spindump of the VM process (process name is the same as VM name).
Also, to work around this you can free another vCPU core to host system to allow Parallels Desktop better virtualize real-time devices (USB, sound and disk I/O) operations properly for the stable guest OS performance (currently 7 of 8 cores are assigned to VM).
Will be waiting for the spindump, and thank you in advance!