High CPU utilization in vnc mode

[Anuj Kalia]

We start a gentoo guest using ./x86-64-softmmu/qemu-x86-64 -hda <disk>.qcow2 -vnc :6.

Then we start a vncviewer session to this guest from a remote computer. In this session, we start a video. After starting the video, the CPU utilization of the guest (the qemu-x86-64 process) increases to about 90%. The high CPU utilization persists even after closing the vncviewer session.

However, the CPU usage while running a video inside a gentoo guest (without a remote computer connecting via vncviewer) is only 20-30%. So we suspect the high CPU usage to be due to the vncserver code running inside QEMU which has to do a lot of work to send the framebuffer updates to the client.

My question is why does the usage not decrease when the remote vncviewer is disconnected? On simple computers (no virtual guests), the CPU usage of vncserver decreases drastically when the vncviewer client is disconnected. Why does this not happen in the vncserver provided by QEMU (through -vnc :6).

[Thomas Huth (th-huth)]

Triaging old bug tickets ... Can you still reproduce this problem wit the latest release of QEMU (currently version 2.9.0), or could we close this bug nowadays?

[Launchpad Janitor (janitor)]

[Expired for QEMU because there has been no activity for 60 days.]