gvfs-afc-volume-monitor is stat'ing /var/run/usbmuxd every second

[Colin Ian King]

I've observed that gvfs-afc-volume-monitor is polling at ~1Hz stat'ing /var/run/usbmuxd

Using eventstat from my PPA: https://launchpad.net/~colin-king/+archive/powermanagement as follows one can identify the thread that is waking up every second:

sudo eventstat 1 1 | grep gvfs-afc
    1.00 2027 gvfs-afc-volume hrtimer_start_range_ns hrtimer_wakeup

and a strace shows:

stat("/var/run/usbmuxd", 0x7faf78339cd0) = -1 ENOENT (No such file or directory)
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
nanosleep({1, 0}, 0x7faf78339dd0) = 0
stat("/var/run/usbmuxd", 0x7faf78339cd0) = -1 ENOENT (No such file or directory)
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0},

Rather than continually polling for /var/run/usbmuxd it is more efficient to use inotify on /var/run and observe any new files appearing and then do the check for /var/run/usbmuxd

Frequent periodical polling reads on the filesystem waste power and reduce the running time on battery.