[Bug 102201] New: fbc causes redraw delays with Qt5 applications.

[bugzilla-daemon at bugzilla.kernel.org]

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.

-- 
You are receiving this mail because:
You are on the CC list for the bug.
You are the assignee for the bug.