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[Bug 1210124] [NEW] qmlscene is busy and there is heap growth when running idle apps

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From: Launchpad Bug Tracker <1210124@xxxxxxxxxxxxxxxxxx>
Date: Sat, 09 Dec 2017 07:52:07 -0000
Reply-to: Bug 1210124 <1210124@xxxxxxxxxxxxxxxxxx>
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You have been subscribed to a public bug:

I've been using health-check from my PPA (ppa:colin-king/white) to
observe idle states of various phone apps and I'm seeing poll/epoll
spinning at ~10 polls a second and some heap growth even when idle.

1. polling on idle consumes power, although small, it will accumulate when a user has multiple idle apps running
2. the heap growth is slow but will add up if an app is running for many hours.

 Attached is the system activity on two idle apps:

1. /usr/lib/arm-linux-gnueabihf/qt5/bin/qmlscene /usr/share/ubuntu-
filemanager-app/ubuntu-filemanager-app

2.  /usr/lib/arm-linux-gnueabihf/qt5/bin/qmlscene /usr/share/ubuntu-
calculator-app/ubuntu-calculator-app

I'm observing:

Top polling system calls:
  PID  Process              Syscall             Rate/Sec   Infinite   Zero     Minimum    Maximum    Average
                                                           Timeouts Timeouts   Timeout    Timeout    Timeout
  2666 qmlscene             poll                    5.6278        0        4   0.0 sec    3.0 sec    1.7 sec 
  2674 qmlscene             epoll_wait              4.9650        0        0   5.0 sec    5.0 sec    5.0 sec 
  2686 qmlscene             epoll_wait              0.2000        0        0   5.0 sec    5.0 sec    5.0 sec 
 Total                                             10.7928        0        4

so ~10Hz of polling.

Also, heap growth:

Change in memory (K/second):
  PID  Process              Type        Size       RSS       PSS
  2666 qmlscene             Heap        0.00      0.39      0.39 (growing slowly)

Since the RSS + PSS are growing I guess this is an anonymous mem-mapped
region that is slowly filling up and populating physical pages and at
sometime we may run out and the underying user space memory allocator
will map a larger region for more heap. But as it is, it seems that the
physical pages are slowly getting used which generally points to a slow
leak somewhere.  I suggest running valgrind on qmlscene to see if it can
spot any heap leakages.

** Affects: qtdeclarative-opensource-src (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: mobile-power-consumption rls-s-incoming
-- 
qmlscene is busy and there is heap growth when running idle apps
https://bugs.launchpad.net/bugs/1210124
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