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

 

So I added some debugging output to dbus.  When it peaked, it spent over
a third of the CPU entirely in get_recipients_from_list().  (This is
dbus checking if an incoming signal matches any of the rules added by
org.freedesktop.DBus.AddMatch -- i.e. signal subscriptions.  It does
this for every rule, for every connection.)

So we can reduce the time spent there by being more efficient, by
reducing the number of subscriptions, or reducing the number of signals.

Looking at which rules it's checking, the majority are subscriptions on
NetworkManager.  One per access point, one per device, from multiple
connections.  Could connectivity-cpp be a bit too subscription-greedy?

I'm not sure that get_recipients_from_list is the only (or worst)
culprit here.  Just something I noticed.

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https://bugs.launchpad.net/bugs/1480877

Title:
  Access points' "PropertiesChanged" dbus signals freeze UI on mobile
  devices

Status in Canonical System Image:
  Confirmed
Status in indicator-network package in Ubuntu:
  Incomplete
Status in network-manager package in Ubuntu:
  Incomplete

Bug description:
  Krillin, rc-proposed, r83

  
  DESCRIPTION:
  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:
  http://pastebin.ubuntu.com/11992322/

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

  HOW TO REPRODUCE: 
  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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References