Hi,

this week I installed multiple laptops with Debian Bullseye and was
wondering why the battery lifetime was so bad.

The cause was obvious upon first glance into htop: redshift-gtk was
running for GDM's GTK greeter, but instead of working correctly it was
constantly consuming 100% power of one CPU core.

After killing redshift-gtk, the battery lifetime quadrupled.

redshift-gtk should either not be launched for the "Debian-gdm" user or work
correctly in the GDM GTK greeter session.

Note: this only affects Bullseye (and probably Sid),
on Buster this issue is non-existent as redshift-gtk does not
start with the GDM GTK greeter session.

Regards
Philipp