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<base href="https://bugs.freedesktop.org/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Very slow Xorg performace when drawing Qt5's QPainter"
href="https://bugs.freedesktop.org/show_bug.cgi?id=89233">89233</a>
</td>
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<th>Summary</th>
<td>Very slow Xorg performace when drawing Qt5's QPainter
</td>
</tr>
<tr>
<th>Product</th>
<td>xorg
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>x86-64 (AMD64)
</td>
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<th>OS</th>
<td>Linux (All)
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
</td>
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<th>Component</th>
<td>Driver/Radeon
</td>
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<th>Assignee</th>
<td>xorg-driver-ati@lists.x.org
</td>
</tr>
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<th>Reporter</th>
<td>madcatx@atlas.cz
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>xorg-team@lists.x.org
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=113671" name="attach_113671" title="MWE">attachment 113671</a> <a href="attachment.cgi?id=113671&action=edit" title="MWE">[details]</a></span>
MWE
My Qt5 based application updates contents of a widget as the mouse moves over
it. Unfortunately the drawing operation causes inexplicably high load and
everything slows down to a crawl. During that time I observe Xorg fully loading
one CPU core, the application itself does not seem to consume much CPU. My
entire desktop is almost unusable until Xorg sorts itself out after a few
seconds.
As of now I found two possible workarounds:
1) Use Qt4 toolkit instead of Qt5
2) Set "Option" "NoAccel" to "true" in Xorg.conf
I believe that this issue has to do with either GLAMOR or xf86-ati drivers
because the application behaves normally on a machine with nVidia card or in
Windows.
I attached a small MWE which demonstrates the problem. Build the MWE with Qt5
toolkit, maximize the window and move mouse over the green area.
Up-to-date Fedora 21
xorg-x11-server 1.16.3
mesa 10.4.3
xorg-x11-drv-ati 7.5.0</pre>
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