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[Bug 1480877] Re: Access points' "PropertiesChanged" dbus signals freeze UI on mobile devices


Here's some test results from me.  tl;dr stopping location services
helps a lot, but still tiny UI stuttering.

My routine is to leave my apartment and walk down the street.  This
means I go from wifi to 3G.  What happens on current images is:

1) As my phone notices that I'm out of wifi range, it freaks out.  This
is when the UI stutters (and high dbus CPU).  This can last up to a
minute, making the phone nigh unusable for the duration.  The indicator
switches to 3G only after all the stuttering stops (making me think it's
finally caught up to all the dbus traffic that's been trying to get
through the loaded dbus).

2) Every so often after this (15 or 30 seconds maybe?), I get a very
brief, maybe 1s, UI stutter.  Presumably this is during wifi scans.  It
goes away if I turn off wifi completely.

I don't see either of those issues when I'm on wifi.  It's only going to
3G and staying on 3G that cause the problems.  Again, everything points
to wifi scans triggering it.

So that's the normal routine.  Today I tried that routine once to
confirm it was still happening.  Then turned off the three services per
comment 56.  And did my routine again.  This time the switch to 3G
happened faster.  I still saw some stuttering during the transition.
Maybe three short bursts of stutter in quick succession.  But all over
in a matter of seconds, versus the minute before.  And I still saw the
regular-interval 1s stutter during normal scans.

But disabling locations was a huge help.  And makes this bug go from a
show-stopper to merely a regular annoyance.

Shall we spin off a bug for the location folks to clean up their dbus

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  Access points' "PropertiesChanged" dbus signals freeze UI on mobile

Status in Canonical System Image:
Status in indicator-network package in Ubuntu:
Status in network-manager package in Ubuntu:
Status in location-service package in Ubuntu RTM:
Status in network-manager package in Ubuntu RTM:

Bug description:
  Krillin, rc-proposed, r83

  I've been trying to track down the cause of the occasional UI freezes on my Krillin device, and I noticed that whenever the UI freezes for 2-4 seconds, I get a burst of "PropertiesChanged" signals in dbus-monitor

  Here's a log of what's shown in dbus-monitor:

  I'd guess the problem is in the code that actually catches the signals
  and acts accordingly.

  1) Move to a place where many wifi hotspots are available
  2) Connect the device via USB and run "phablet-shell" and then "dbus-monitor"
  3) Use the device while keeping an eye on dbus-monitor output

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