已解决:

/etc/systemd/system.conf

/etc/systemd/user.conf

DefaultTimeoutStartSec=10s
DefaultTimeoutStopSec=10s

之前只改了system.conf，发现user.conf了也是同样的参数，一起改了就生效了。。。

最终解决：

参考方案

You need to both disable the autostarter AND mask the user bus service, or it will get started anyway. First, make sure your autostart override directory exists with this command:
mkdir -v ~/.config/autostart
Then you can run this command to disable the autostarter:
cat /etc/xdg/autostart/at-spi-dbus-bus.desktop <(echo "X-GNOME-Autostart-enabled=false") > ~/.config/autostart/at-spi-dbus-bus.desktop
Finally also mask the user bus service:
systemctl --user mask at-spi-dbus-bus.service