Battery drain (upowerd high CPU) on Nexus 4 when no network is available

[Dubstar_04]

Nexus 4 connected to wifi but not logged in so no network available. Battery drained from full to empty in 6 hours, with no use.

rc_proposed
Image Part: 10160714
Build No: R486
Device Image Part: 20160404.1

[Dubstar_04 (dubstar-04)]

Top output attached.

[Alexandros Frantzis (afrantzis)]

The top output doesn't implicate repowerd. Note, however, that the top output is incomplete so we don't have the whole picture. For future reference you can take textual snapshots of top with:

top -b -n10 -d1 > /tmp/top.txt

(Write to file 10 textual snapshots with 1 sec delay between snapshots)

If you come across this problem again, please provide the output of the command above.

From the provided top screenshot, it's interesting to note that the total CPU times for unity8 and upowerd are very high relative to the uptime, so the cause of the drain could be in one of these components.

[Daniel van Vugt (vanvugt)]

Unity8 doesn't idle efficiently, which is also bug 1479250. In this case however the user is displaying the top output on the screen so Unity8 CPU will be significantly higher than in bug 1479250, which is expected.

Let's try to keep this bug primarily about the main offender: upowerd. Unity8 already has a few people working on performance improvements.

[Pat McGowan (pat-mcgowan)]

please provide a syslog for the period with battery drain