Chrome OS Inactivity Delays

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By default, the power manager performs various actions when the system is inactive for a given period of time:

Power sourceSmart DimDim screenTurn screen offSuspend / sleep
Batteryearly5 minutes5.5 minutes6.5 minutes
ACearly7 minutes7.5 minutes8.5 minutes
Batterydefer10 minutes10.5 minutes11.5 minutes
ACdefer14 minutes14.5 minutes15.5 minutes

At the half point of inactivity delay, the Smart Dim ML model will predict whether the user is likely to remain inactive and tell powerd to dim screen early or defer dim accordingly.

There are different ways to define “activity”:

  • User activity (keyboard or touchpad events or other events that indicate a human is present, like changing the power source or connecting or disconnecting an external display)
  • Video activity (currently defined as 15 or more 333x250 or larger updates within a second in an active tab in an onscreen window)
  • Audio activity (currently defined as active output streams)

User activity and video activity block all of the above actions from being performed. The screen will still dim and be turned off while audio is being played, but the system will not suspend. Once activity ceases, the inactivity timer starts again.

When the suspend delay is reached while no user is logged in and the system is on battery power, the system will shut down instead of suspending.

As of M41, if the lock screen is displayed, the screen will be dimmed after just 30 seconds of inactivity and turned off after 40 seconds as described in issue 190499.

Several events can result in the above delays being lengthened (specifically, the screen-dimming delay is doubled and the other delays' distances from the dimming delay are maintained; for example, on battery, the delays are changed to 10/11/15 minutes):

  • An external monitor is connected
  • User activity occurs while the screen is dimmed or soon after it is turned off (delays are reset after the current user logs out)

If the “Require password to wake from sleep” setting is enabled, the screen will be locked ten seconds after the screen is turned off due to inactivity (in addition to being locked immediately before the system suspends when the lid is closed).

As of M71, an ML model has been enabled to run in Chrome to predict whether a screen dim should be deferred. When powerd is about to dim the screen in response to user inactivity, the model will predict whether the user is likely to reactivate the device after dimming. If reactivation seems likely, Chrome will tell powerd to defer dimming. To reduce the risk of incorrect predictions keeping the system awake indefinitely, dimming will only be deferred once until the user begins interacting with the system again. When the model is enabled, powerd's delay-doubling behavior for “presentation mode” or user activity is disabled.

The above delays and actions can be configured by Chrome and are sent to the power manager as PowerManagementPolicy protocol buffers via D-Bus. Chrome's settings are controlled by “Power management” enterprise policies and by the chrome.power extension API.

On a running system, /var/log/power_manager/powerd.LATEST should contain enough details to understand why a given action was taken. This file is accessible via chrome://system or by browsing to file://var/log.

Further reading

  • src/platform/system_api/dbus/power_manager/policy.proto: definition of PowerManagementPolicy protocol buffer
  • src/platform2/power_manager/powerd/policy/state_controller.{h,cc}: StateController class in power manager; responsible for managing delays