[Bug 102201] New: fbc causes redraw delays with Qt5 applications.
bugzilla-daemon at bugzilla.kernel.org
bugzilla-daemon at bugzilla.kernel.org
Sat Aug 1 20:03:12 PDT 2015
https://bugzilla.kernel.org/show_bug.cgi?id=102201
Bug ID: 102201
Summary: fbc causes redraw delays with Qt5 applications.
Product: Drivers
Version: 2.5
Kernel Version: 4.1.3
Hardware: All
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Video(DRI - Intel)
Assignee: intel-gfx-bugs at lists.freedesktop.org
Reporter: francis.herne at yahoo.co.uk
CC: intel-gfx-bugs at lists.freedesktop.org
Regression: No
First off - I'm aware that this is an experimental feature that shouldn't be
expected to work.
When 'i915.enable_fbc=1' is specified on the kernel cmdline, and a
non-compositing window manager is used, Qt5-based applications experience
frequent periods (more than half the time) of 5-10 seconds when their windows
are not redrawn. Other (non-Qt5-based) apps running at the same time are not
affected.
When using non-compositing WMs (either dwm 6.0 or openbox 3.6.1), this occurs
for every instance of every Qt5-based application that I've tried, across
several reboots, and never for applications using other GUI toolkits including
GTK2, FLTK and Qt4.
When using a compositing WM, this never occurs even when fbc is enabled. This
includes KWin with either backend or Compton+openbox - in the latter case, the
delays immediately cease when compton is started.
This never occurs when framebuffer compression has not been enabled, regardless
of toolkit or WM.
I can't see any related output in the system journal, dmesg, stderr of the
applications or Xorg log files.
I'm using the standard ArchLinux kernel build 4.1.3-1-ARCH, with Qt 5.5.0, mesa
10.6.3 and Xorg 1.17.2. The hardware is a Thinkpad X201, with an i5-580M
(Ironlake) and its integrated graphics and a 1280x800 LVDS display.
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