VM start causes keyboard lag

[3hhh]

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Qubes OS release

4.2

Brief summary

Since a few months I noticed that starting a VM causes keyboard lag in dom0.

Steps to reproduce

1. Start a VM.
2. Repeat the Mod-R, Return key combination in my dom0 window manager (qtile).
3. At some point the window manager doesn't receive the key combination anymore for a short time frame.

Expected behavior

Short response time to keyboard input.

Actual behavior

Lag.

Additional information

• I noticed via iotop that the lag usually happens when qrecec-client and pacat-simple-vchan have the most I/O and disappears afterwards.
• I tested this via a PS/2 keyboard.
• Possibly related: #9603, #9629, #8636, ...