location service is waking up at 10Hz causing possible unwanted wakeups

[Colin Ian King]

I've observed that location service is waking up ~10 times per second due to a 100ms sleep

ps -ax | grep 2295
 2295 ? Ssl 0:00 /usr/bin/ubuntu-location-serviced --bus system --provider gps::Provider

eventstat shows it's the top waking userspace process on the phone:

root@ubuntu-phablet:/# eventstat 300 1
 Event/s PID Task Init Function Callback
    9.99 2304 ubuntu-location hrtimer_start_range_ns hrtimer_wakeup

health-check shows that this is occuring in a 100ms nanosleep() system call.

Attached is the output from health-check. Is is possible to use a select() or poll() rather than a 10Hz non-blocking delay loop to reduce polling wakeups?

[Thomas Voß (thomas-voss)]

I tried to reproduce the wakeups with the location service being idle -> no wakeups
Whenever the location engine is started, though, the chipset driver wakes up regularly roughly at the reported interval. I would like to patch that behavior, but the chipset driver is unfortunately a binary blob.

[Colin Ian King (colin-king)]

BTW, which binary blob is the chipset driver? i don't mind looking at it and seeing if we can "tweak" it a bit.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

Confirmed. Even after turning off all location services, this continues to have the highest number of wakeups of any user service:

$ sudo eventstat
 Event/s PID Task Init Function Callback
   26.00 0 [swapper/0] hrtimer_start_range_ns tick_sched_timer
   20.00 0 [swapper/0] hrtimer_start tscpu_update_tempinfo
   20.00 22750 [kworker/0:0] OSTimerWorkQueueCallBack OSTimerCallbackWrapper
   10.00 2556 ubuntu-location hrtimer_start_range_ns hrtimer_wakeup <------------------------------------------------
    8.00 0 [swapper/0] hrtimer_start tick_sched_timer
    5.00 25671 unity8 hrtimer_start_range_ns hrtimer_wakeup
    3.00 57 [hps_main] _hps_task_main process_timeout
    2.00 1370 gmain hrtimer_start_range_ns hrtimer_wakeup
    2.00 25706 ubuntu-push-cli hrtimer_start_range_ns hrtimer_wakeup
    1.00 1 [swapper/0] start_bandwidth_timer sched_rt_period_timer
    1.00 0 [swapper/0] mlog_timer_handler mlog_timer_handler
    1.00 1879 [tx_thread] __pm_wakeup_event pm_wakeup_timer_fn
    1.00 22750 [kworker/0:0] osal_timer_modify _stp_psm_stp_is_idle
    1.00 15947 sshd sk_reset_timer tcp_write_timer
    1.00 25751 ubuntu-push-cli hrtimer_start_range_ns hrtimer_wakeup
    1.00 0 [swapper/0] add_timer wmt_cal_stats
    1.00 847 6620_launcher hrtimer_start_range_ns hrtimer_wakeup
    1.00 22750 [kworker/0:0] schedule_timeout_uninterruptible process_timeout
    1.00 1 [swapper/0] hrtimer_start charger_hv_detect_sw_workaround
106 Total events, 106.00 events/sec (kernel: 84.00, userspace: 22.00)

The PID is deceiving. It's actually a thread of a different PID which is /usr/bin/ubuntu-location-serviced

$ system-image-cli -i
current build number: 94
device name: arale
channel: ubuntu-touch/rc-proposed/ubuntu
last update: 2015-08-28 07:44:31
version version: 94
version ubuntu: 20150828
version device: 20150818-0b38025
version custom: 20150828

[Thomas Voß (thomas-voss)]

I'm not saying that it's not waking up, just pointing out that we have no way of fixing the source of the wakeups for now. Lowering priority.