[Digikam-devel] [Bug 231849] New: digikam wakes up 107 times per second (powertop)

[Stefan Fleiter]

https://bugs.kde.org/show_bug.cgi?id=231849

           Summary: digikam wakes up 107 times per second (powertop)
           Product: digikam
           Version: 1.1.0
          Platform: Ubuntu Packages
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: digikam-devel at kde.org
        ReportedBy: stefan.fleiter at web.de


Version:           1.1.0 (using KDE 4.4.1)
OS:                Linux
Installed from:    Ubuntu Packages

digikam wakes up the cpu more than 100 times per second
without any user activity.
There are no special steps to reproduce, simply start digikam.

That makes digikam almost unusable on laptops when running on battery.

I will attach a strace log which shows it does busy waiting
by means of select and poll and does read from a file descriptor (7)
which points to a unix domain socket in spite of the fact that
the matching poll returned with a timeout.

# ls -l /proc/3182/fd/7
lrwx------ 1 me me 64 2010-03-22 22:25 /proc/3182/fd/7 -> socket:[33307]
# lsof | grep 33307
digikam   3182        me    7u     unix 0xffff8800df785200      0t0    33307
socket


Here the powertop output:

# sudo powertop -d
PowerTOP 1.12   (C) 2007, 2008 Intel Corporation 

Collecting data for 15 seconds 


Cn                Avg residency
C0 (cpu running)        (10.9%)
polling           0.0ms ( 0.0%)
C1 mwait          0.0ms ( 0.0%)
C2 mwait          0.1ms ( 0.2%)
C4 mwait          1.8ms (88.9%)
P-states (frequencies)
Turbo Mode     4.3%
  2.21 Ghz     0.0%
  1.60 Ghz     0.1%
  1200 Mhz     0.1%
   800 Mhz    95.5%
Wakeups-from-idle per second : 495.4    interval: 15.0s
no ACPI power usage estimate available
Top causes for wakeups:
  29.7% (232.7)   [Rescheduling interrupts] <kernel IPI>
  16.9% (132.6)   firefox-bin
  13.7% (107.1)   digikam
  12.5% ( 98.1)   [extra timer interrupt]
  10.7% ( 83.9)   [kernel scheduler] Load balancing tick

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