[PyQt] QGraphicsView very slow under Linux and Mac OS X

[Clemens Brunner]

On 04/03/2013 06:46 PM, Hans-Peter Jansen wrote:

> Which graphic driver do you use? (that doesn't tell us much, since the C++
> version behave with the same driver, just for the record..)

xf86-video-intel 2.21.5-1
intel-dri 9.1.1-1

> Might be worth to compare the C++ version (that you should publish here¹)
> and the Python versions with perf. Of course, they differ...

Attached.

> python versions, perf running for about 10 sec.
>
> QT_GRAPHICSSYSTEM=raster perf record -f python graphicsviewtest.py
>
> [...]
>
>
> QT_GRAPHICSSYSTEM=opengl perf record -f python graphicsviewtest.py
>
> [...]
>
>
> The former looks nice, it's a great example, why PyQt rocks. The hottest
> areas are there, where they should be: down under, moving bits. Great.
>
> But the latter looks strange indeed.
>
> Phil, do you have any idea, why PyEval_EvalFrameEx is the top sucker in
> this scenario? This looks, like in opengl mode, it is evaluating some
> python expression in its hottest path (data type conversions or the like?).

My raster perf report doesn't look nice at all:

  14.30%  python2  libpython2.7.so.1.0       [.] PyEval_EvalFrameEx
   9.39%  python2  libQtGui.so.4.8.4         [.] 0x00000000001bf673
   8.99%  python2  sip.so                    [.] 0x000000000000b086
   6.10%  python2  libpython2.7.so.1.0       [.] lookdict_string
   4.02%  python2  libpython2.7.so.1.0       [.] PyDict_GetItem
   3.94%  python2  libpython2.7.so.1.0       [.] _PyType_Lookup
   3.01%  python2  libm-2.17.so              [.] 0x00000000000105e0
   2.27%  python2  libm-2.17.so              [.] feraiseexcept
   2.23%  python2  libpython2.7.so.1.0       [.] _PyObject_GenericGetAttrWithDict
   1.71%  python2  libpython2.7.so.1.0       [.] binary_op1
   1.50%  python2  libpython2.7.so.1.0       [.] PyType_IsSubtype
   1.40%  python2  libpython2.7.so.1.0       [.] PyErr_Restore
   1.33%  python2  QtGui.so                  [.] 0x000000000036120b
   1.27%  python2  libpython2.7.so.1.0       [.] PyObject_Malloc
   1.19%  python2  libc-2.17.so              [.] malloc

Same thing but even worse with opengl:

  15.49%  python2  i965_dri.so               [.] 0x000000000003ae99
   6.08%  python2  libpython2.7.so.1.0       [.] PyEval_EvalFrameEx
   5.96%  python2  libdrm_intel.so.1.0.0     [.] 0x0000000000007468
   5.60%  python2  libQtOpenGL.so.4.8.4      [.] 0x0000000000031262
   4.96%  python2  sip.so                    [.] 0x000000000000b055
   4.32%  python2  libdricore9.1.1.so.1.0.0  [.] 0x00000000001ea2b4
   2.76%  python2  libpython2.7.so.1.0       [.] lookdict_string
   2.11%  python2  libpython2.7.so.1.0       [.] PyDict_GetItem
   1.95%  python2  libpython2.7.so.1.0       [.] _PyType_Lookup
   1.42%  python2  libm-2.17.so              [.] 0x00000000000105c0
   1.32%  python2  libc-2.17.so              [.] __memcmp_sse4_1
   1.03%  python2  libc-2.17.so              [.] _int_malloc
   1.01%  python2  libm-2.17.so              [.] feraiseexcept
   0.93%  python2  libc-2.17.so              [.] __memcpy_ssse3_back

In both cases, PyEval_EvalFrameEx is at or near the top, and so are other Python things.

For the sake of completeness, here's the perf output for the C++ version (which runs perfectly):

  43.56%  graphicsviewtes  libQtGui.so.4.8.4         [.] 0x00000000001c0bb2                                   q
  20.58%  graphicsviewtes  libm-2.17.so              [.] feraiseexcept
  15.48%  graphicsviewtes  libm-2.17.so              [.] 0x0000000000015622
   4.47%  graphicsviewtes  graphicsviewtest          [.] SignalItem::paint(QPainter*, QStyleOptionGraphicsItem
   3.09%  graphicsviewtes  libQtGui.so.4.8.4         [.] QPen::dashPattern() const
   1.17%  graphicsviewtes  libQtGui.so.4.8.4         [.] QTransform::map(QPointF const&) const
   0.77%  graphicsviewtes  libc-2.17.so              [.] free
   0.72%  graphicsviewtes  libQtGui.so.4.8.4         [.] QPainter::drawLines(QLine const*, int)
   0.46%  graphicsviewtes  libpthread-2.17.so        [.] __pthread_mutex_unlock_usercnt
   0.45%  graphicsviewtes  libpthread-2.17.so        [.] pthread_mutex_lock

I tested this program on openSUSE (in a VirtualBox), and in contrast to Vincent, it doesn't work for me there either (same behavior as in my native Arch Linux). BTW, I use KDE and not Gnome, but I doubt that this is relevant. Furthermore, I still have the same bad behavior on my Mac.

Clemens
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######################################################################
# Automatically generated by qmake (2.01a) Tue Mar 19 14:38:49 2013
######################################################################

TEMPLATE = app
CONFIG += console
TARGET = 
DEPENDPATH += .
INCLUDEPATH += .

# Input
SOURCES += graphicsviewtest.cpp