Public bug reported:
I was wondering why I was seeing lots of wakeup events on my idle system
and tracked it down to containerd. Running eventstat for 1 sample over
a 10 second interval one can observed that containerd is waking the
system up nearly 10 times a second:
sudo eventstat 10 1
Event/s PID %CPU PR NI Task Init Function
13.45 2554 0.0 0 0 Xorg it_real_fn
9.53 1539 0.0 0 0 containerd hrtimer_wakeup
8.23 8862 0.0 0 0 Timer hrtimer_wakeup
stracing the process one can see rapid futex/pselect calls:
futex(0x55fad4c61010, FUTEX_WAIT, 0, {tv_sec=60, tv_nsec=0}) = 0
pselect6(0, NULL, NULL, NULL, {tv_sec=0, tv_nsec=20000}, NULL) = 0 (Timeout)
futex(0x55fad4c61010, FUTEX_WAIT, 0, {tv_sec=60, tv_nsec=0}) = 0
pselect6(0, NULL, NULL, NULL, {tv_sec=0, tv_nsec=20000}, NULL) = 0 (Timeout)
futex(0x55fad4c61010, FUTEX_WAIT, 0, {tv_sec=60, tv_nsec=0}) = 0
pselect6(0, NULL, NULL, NULL, {tv_sec=0, tv_nsec=20000}, NULL) = 0 (Timeout)
futex(0x55fad4c61010, FUTEX_WAIT, 0, {tv_sec=60, tv_nsec=0}) = 0
The pselect6 system call is basically being used as a high resolution
delay of ~20,000 nanoseconds before polling a futex. This is causing the
high amount of system wakeups that stop the CPU from going into a deep C
sleep state and it's eating power. Can this be fixed?
** Affects: containerd (Ubuntu)
Importance: Medium
Status: New
** Changed in: containerd (Ubuntu)
Importance: Undecided => Medium
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https://bugs.launchpad.net/bugs/1826684
Title:
containerd is polling on a pselect ever 20,000 nanoseconds causing
rapid system wakeup events
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