macOS App Nap feature gradually freezes QEMU process

[Vasiliy Nikonov]

macOS version: 10.15.2
QEMU versions: 5.2.0 (from MacPorts)
               5.2.92 (v6.0.0-rc2-23-g9692c7b037)

If the QEMU window is not visible (hidden, minimized or another application is in full screen mode), the QEMU process gradually freezes: it still runs, but the VM does not respond to external requests such as Telnet or SSH until the QEMU window is visible on the desktop.

This behavior is due to the work of the macOS App Nap function:
https://developer.apple.com/library/archive/documentation/Performance/Conceptual/power_efficiency_guidelines_osx/AppNap.html#//apple_ref/doc/uid/TP40013929-CH2-SW1

It doesn't matter how the process is started -- as a background job or as a foreground shell process in case QEMU has a desktop window.

My VM does not have a display output, only a serial line, most likely if the VM was using OpenGL, or playing sound (or any other App Nap triggers), then the problem would never have been detected.

In my case only one starting way without this problem:
sudo qemu-system-x86_64 -nodefaults \
-cpu host -accel hvf -smp 1 -m 384 \
-device virtio-blk-pci,drive=flash0 \
-drive file=/vios-adventerprisek9-m.vmdk.SPA.156-1.T.vmdk,if=none,format=vmdk,id=flash0 \
-device e1000,netdev=local -netdev tap,id=local,ifname=tap0,script=no,downscript=no \
-serial stdio -display none

The typical way from the internet to disable App Nap doesn't work:
defaults write NSGlobalDomain NSAppSleepDisabled -bool YES

[Thomas Huth (th-huth)]

The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting the bug state to "Incomplete" now.

If the bug has already been fixed in the latest upstream version of QEMU,
then please close this ticket as "Fix released".

If it is not fixed yet and you think that this bug report here is still
valid, then you have two options:

1) If you already have an account on gitlab.com, please open a new ticket
for this problem in our new tracker here:

    https://gitlab.com/qemu-project/qemu/-/issues

and then close this ticket here on Launchpad (or let it expire auto-
matically after 60 days). Please mention the URL of this bug ticket on
Launchpad in the new ticket on GitLab.

2) If you don't have an account on gitlab.com and don't intend to get
one, but still would like to keep this ticket opened, then please switch
the state back to "New" or "Confirmed" within the next 60 days (other-
wise it will get closed as "Expired"). We will then eventually migrate
the ticket automatically to the new system (but you won't be the reporter
of the bug in the new system and thus you won't get notified on changes
anymore).

Thank you and sorry for the inconvenience.

[Thomas Huth (th-huth)]

Moved here:
https://gitlab.com/qemu-project/qemu/-/issues/334