As discussed in  issue 875952 , ARC startup frequently takes 90+ seconds on edgar (and other devices? I'm not sure that anyone is measuring this). This doesn't happen every time; sometimes it's ~30 seconds.

I'm attaching some ARC logs from fast and slow runs of the arc.Boot Tast test on edgar-paladin. I've rewritten all timestamps as offsets from the first entry to make the files easier to compare.

I'm unfamiliar with Android bootup, but one consistent difference is that in fast runs, messages about /sys/class/android_usb/android0 and arc-ureadahead-trace are logged soon after arcbridgeservice is started:

 30.618 NOTICE arc-kmsg-logger[5136]: <5>init: Starting service 'arcbridgeservice'...
...
 36.867 NOTICE arc-kmsg-logger[5136]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/enable': No such file or directory
 36.867 NOTICE arc-kmsg-logger[5136]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/idVendor': No such file or directory
 36.867 NOTICE arc-kmsg-logger[5136]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/idProduct': No such file or directory
 36.867 NOTICE arc-kmsg-logger[5136]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/functions': No such file or directory
 36.867 NOTICE arc-kmsg-logger[5136]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/enable': No such file or directory
 38.571 INFO arc-networkd[5467]: [INFO:router_finder.cc(57)] No IPv6 router found on iface eth1
 38.777 NOTICE arc-ureadahead-trace[6174]: Post-stop arc-ureadahead-trace
...
 39.227 NOTICE arc-kmsg-logger[5136]: <5>init: Starting service 'adbd'...

---

In slow runs, there's a ~1-minute delay before these messages are logged:

 28.913 NOTICE arc-kmsg-logger[7370]: <5>init: Starting service 'arcbridgeservice'...
...
 36.782 INFO arc-networkd[7522]: [INFO:router_finder.cc(57)] No IPv6 router found on iface eth0
 91.612 NOTICE arc-kmsg-logger[7370]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/enable': No such file or directory
 91.612 NOTICE arc-kmsg-logger[7370]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/idVendor': No such file or directory
 91.612 NOTICE arc-kmsg-logger[7370]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/idProduct': No such file or directory
 91.612 NOTICE arc-kmsg-logger[7370]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/functions': No such file or directory
 91.612 NOTICE arc-kmsg-logger[7370]: <5>init: write_file: Unable to open '/sys/class/android_usb/android0/enable': No such file or directory
 93.581 NOTICE arc-ureadahead-trace[8910]: Post-stop arc-ureadahead-trace
...
 93.987 NOTICE arc-kmsg-logger[7370]: <5>init: Starting service 'adbd'...


 

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