31 December, 2007

Last Performance Blog

According to a reply on my previous blog, I could just as well test if having my hamster run in his wheel would increase drawingspeed as long as I don't use valgrind and cachegrind.

Well, I've never used those tools before, but hey. Let's give it a try.

Valgrind and Dolphin (resizing all the time).
Well, valgrind talked about memleaks. I get that. The details of that, however, don't tell me much (of course, that's an understatement).

==21180== LEAK SUMMARY:
==21180== definitely lost: 8,383 bytes in 342 blocks.

The output for individual parts where something is lost is like this:
==21180== 216 bytes in 1 blocks are definitely lost in loss record 175 of 257
==21180== at 0x4021765: malloc (in /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so)
==21180== by 0x56BB885: _XimOpenIM (in /usr/lib/libX11.so.6.2.0)
==21180== by 0x56B88CF: _XimRegisterIMInstantiateCallback (in /usr/lib/libX11.so.6.2.0)
==21180== by 0x5699517: XRegisterIMInstantiateCallback (in /usr/lib/libX11.so.6.2.0)
==21180== by 0x503F73D: QXIMInputContext::QXIMInputContext() (qximinputcontext_x11.cpp:361)
==21180== by 0x503E4A5: QInputContextFactory::create(QString const&, QObject*) (qinputcontextfactory.cpp:120)
==21180== by 0x4B928F1: QApplication::inputContext() const (qapplication.cpp:4541)
==21180== by 0x4BD5046: QWidget::inputContext() (qwidget.cpp:245)
==21180== by 0x4C051CC: QWidget::destroy(bool, bool) (qwidget_x11.cpp:853)
==21180== by 0x4BD7D8F: QWidget::~QWidget() (qwidget.cpp:1264)
==21180== by 0x4EADB04: QLineEdit::~QLineEdit() (qlineedit.cpp:357)
==21180== by 0x4E76C8A: QComboBox::setLineEdit(QLineEdit*) (qcombobox.cpp:1599)

Above is with QtCurve as style, btw.

Well, I think that would explain it all if I just had more brains. Unfortunately, I don't, so let's go on to kcachegrind. Again with QtCurve, which, as I mentioned before, draws a bit faster than Oxygen.

Well, what can I say. Lovely graphs, that's for sure. As far as I can tell, this tool shows where the app is spending it's time. I guess the 100% ld-2.7.so doesn't mean that's what the app does all the time.
The < cycle 13 > I see as LibQtCore.so.4.4.0 doesn't explain much either. Digging down (this kcallgrind tool is pretty cool, even though I don't really understand it) I seem to see a lot of calls to QWidgetBackingStore?!? And there are over 2.4 million calls to isPaintOrScrollDoneEvent, but the % spend there (if that's what the % mean) is just 1.5%... Hmmm, again - big ?????

Or is that second line, self, the one which shows how much a function is called? Sounds like it could be true. In that case, at least 12% of the time of Dolphin (when resizing all the time, of course) is spend in varous libc-2.7.so calls.
The funny thing is that the orders for the libc-2.7.so functions seem to come all from the same Qt function: QListView::paintEvent < cycle 13 >. And then some KFileitemDelegate::paint things.

This could mean QListView is the problem (did I say something about QScrollBar? Does that have something to do with QListView?)? Or does this mean my hamster simply didn't run fast enough?

I'm sorry. This does not make anything clear to me. As I said before, I'm going to wait for someone actually knowledgeable in this area to say something.

A commenter on my previous blog did use callgrind, btw, but his findings were not very clear (to him, I mean, they were obviously not clear to me anyway).

Luckily I received also a few private mails, ranging from "Xephyr does indeed weird stuff, Qt4 apps draw much faster in it than in plain X" to "go on blogging about this". Which I won't, btw, as I never intended to go this far. Sure, many ppl seem to find it interesting, but the complaints about "don't whine, do something", while not making me happy, have a point. I can't do anything, so someone who actually CAN should take over. Or not, in that case - well. Shit happens. Maybe just use GTK apps, then. I had to install a bunch of GTK libs for kcachegrind anyway, for some weird reason:
libgnomecanvas, libgnome, libbonoboui, gnome-keyring, libgnomeui, graphviz, gail, gconf, gnome-vfs and libbonobo (including a bunch of errors about missing gtk things and other stuff, even though kcachegrind works fine)
Why KCachegrind needed that stuf: please let me know. I'd love to get rid of it again.

Edit: aah, probably optional (but apparently compiled in) dependencies of Graphviz... Weird, the graphviz page doesn't mention them, so I still think it's faulty.... So far for Arch linux is mean & lean.

Oh, and Happy new year for those who already are in 2008 when they read this ;-)

Edit2: And the Gwenview author, Aurélien Gâteau, just emailed me to ask me to test some improvements to the panning in Gwenview 4 he made in response to my blogs. So I did test it, and I am happy to tell you all the slower panning in Gwenview in KDE 4 is totally gone - the KDE 4 version is now as fast as the KDE 3 version! Thank you, Aurélien!

Edit3: make the blog sound less like I'll be crying all night because someone said bad things - after all, that's not the point, and I don't want to sound like I won't blog anymore if ppl are mean...