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Running eventstat for 1 sample over a period of 60 seconds, I see that
powerd is generating 2 wakeups every second:
root@ubuntu-phablet:/# eventstat 60 1
Event/s PID Task Init Function Callback
35.98 0 [swapper] cpufreq_interactive_idle_end
cpufreq_interactive_timer
20.95 0 [swapper] hrtimer_start tick_sched_timer
8.55 0 [swapper] hrtimer_start_range_ns tick_sched_timer
3.95 568 SurfaceFlinger hrtimer_start_range_ns hrtimer_wakeup
2.00 711 void android::I hrtimer_wakeup
2.00 1386 powerd hrtimer_start_range_ns hrtimer_wakeup
strace -p 1386
Process 1386 attached - interrupt to quit
clock_gettime(CLOCK_MONOTONIC, {30785, 822251534}) = 0
epoll_wait(0x16, 0x45f37b90, 0x10, 0x1f4) = 0
clock_gettime(CLOCK_MONOTONIC, {30786, 324570870}) = 0
epoll_wait(0x16, 0x45f37b90, 0x10, 0x1f4) = 0
clock_gettime(CLOCK_MONOTONIC, {30786, 826829170}) = 0
epoll_wait(0x16, 0x45f37b90, 0x10, 0x1f4) = 0
clock_gettime(CLOCK_MONOTONIC, {30787, 329179022}) = 0
epoll_wait(0x16, 0x45f37b90, 0x10, 0x1f4) = 0
clock_gettime(CLOCK_MONOTONIC, {30787, 831437324}) = 0
epoll_wait(0x16, 0x45f37b90, 0x10, 0x1f4) = 0
clock_gettime(CLOCK_MONOTONIC, {30788, 332932685}) = 0
So, the culprit is the epoll_wait for 0x1f4 milleseconds (500
milliseconds). epoll_wait is polling on fd 22 which according
/proc/../fd is:
lrwx------ 1 root root 64 Jul 18 10:17 22 -> anon_inode:[eventpoll]
I can't see anything obvious in the powerd source, so I guess it's
occuring in g_main_loop_run
Anyhow, this epoll_wait is returning zero, so there has been no activity
on the fd, and it goes back into a polling loop over and over again. I
wonder if there is a way of changing the timeout?
** Affects: libhybris (Ubuntu)
Importance: Medium
Assignee: Ricardo Salveti (rsalveti)
Status: Triaged
** Tags: mobile-power-consumption
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powerd generating 2 wakeups a second on idle on mobile platforms
https://bugs.launchpad.net/bugs/1202619
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