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[Colin King <1221751@xxxxxxxxxxxxxxxxxx>]

** Tags added: mobile-power-consumption

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https://bugs.launchpad.net/bugs/1221751

Title:
  on an idle system indicator-datetime is actually quite busy

Status in The Date and Time Indicator:
  New
Status in The Ubuntu Power Consumption Project:
  New

Bug description:
  I've instrumented indicator-datetime on a Samsung Galaxy Nexus phone
  on the ubuntu-touch images and it is quite a busy programme.

  I ran health-check (http://kernel.ubuntu.com/~cking/health-check)
  against it for 10 minutes and observed some interesting issues:

  1. Quite a lot of active poll calls:

  Top polling system calls:
    PID  Process              Syscall             Rate/Sec   Infinite   Zero     Minimum    Maximum    Average
                                                             Timeouts Timeouts   Timeout    Timeout    Timeout
    1379 indicator-datetime-s poll                    4.5533      492     2240   0.0 sec    0.0 sec    0.0 sec 
    1380 indicator-datetime-s poll                    0.7950       72       72   0.0 sec   25.0 sec   17.5 sec 
    1352 indicator-datetime-s poll                    0.5167       72       11   0.0 sec  180.0 sec   85.7 sec 
    1375 indicator-datetime-s poll                    0.1450       14       12   0.0 sec   25.0 sec   17.5 sec 
   Total                                              6.0100      650     2335

  I guess these are from glib's  g_main_context_poll(), but it does seem
  quite busy.

  2. I think the polling blocking/waking is causing quite a lot of
  context switches:

  Context Switches:
    PID  Process                Voluntary   Involuntary     Total
                               Ctxt Sw/Sec  Ctxt Sw/Sec  Ctxt Sw/Sec
    1379 indicator-datetime-s        29.38         1.27        30.66 (moderate)
    1380 indicator-datetime-s        11.01         0.05        11.06 (moderate)
    1352 indicator-datetime-s         8.52         0.22         8.73 (low)
    1375 indicator-datetime-s         1.87         0.00         1.88 (low)
    1378 indicator-datetime-s         0.00         0.00         0.00 (idle)
   Total                             50.79         1.54        52.33
   
  50 or so a second perhaps could be considered a little excessive for an indicator

  3. Open/Closing of /etc/localtime without actually seemingly reading
  data. Over a 10 minute interval we observe:

  File I/O operations:
    PID  Process               Count  Op  Filename
    1352 indicator-datetime-s    119    C /etc/localtime
    1352 indicator-datetime-s    119    O /etc/localtime
    1352 indicator-datetime-s      2   OC /etc/localtime
   Total                         240

  So that makes an access to /etc/localtime every 5 seconds for no real
  purpose.  This seems like unnecessary activity - why do we need to
  keep peeking at this file every 5 seconds, it doesn't change that
  often ;-)

  For reference, I will add the full health-check report to the bug
  report.

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