https://bugs.freedesktop.org/show_bug.cgi?id=97940
Bug ID: 97940
Summary: Short desktop freezes with Radeon 7850
Product: xorg
Version: unspecified
Hardware: x86-64 (AMD64)
OS: Linux (All)
Status: NEW
Severity: normal
Priority: medium
Component: Driver/Radeon
Assignee: xorg-driver-ati@lists.x.org
Reporter: daniel.lichtenber...@gmail.com
QA Contact: xorg-t...@lists.x.org
Created attachment 126797
--> https://bugs.freedesktop.org/attachment.cgi?id=126797&action=edit
test program to list all connectors
Kernel: openSUSE Tumbleweed 4.7.4-2-default
HW: Radeon 7850 2GB, dual DVI monitors
I have an annoying issue on my Radeon 7850. At some point in
the kernel 4.x timeframe, the entire desktop started to freeze for
short periods (< 1 second), almost exclusively during startup when
the desktop applets/widgets were loading. It's very
noticeable/annoying because the mouse cursor freezes as well.
Aside from the startup freezes that happen every time, the issue
is hard to reproduce (I get also short freezes when opening a PDF
in a new instance of Okular - the KDE PDF viewer).
With the help of perf I stumbled over suspicious traces of DRM
getconnector calls. I hacked together a small program that reproduces
the issue on my system: when run in a loop, I can barely move the
mouse cursor and I get perf traces like the following:
- drm_helper_probe_single_connector_modes
- 45,15% 0,00% drm-getconnecto [kernel.kallsyms]
[k] drm_helper_probe_single_connector_modes
- 41,70% radeon_dvi_detect
- 40,19% radeon_connector_get_edid
- drm_get_edid
- 39,30% drm_do_get_edid
drm_do_probe_ddc_edid
i2c_transfer
__i2c_transfer
- bit_xfer
+ 16,45% sclhi
15,74% delay_tsc
+ 4,39% acknak
1,14% set_clock
0,76% get_data
+ 0,54% try_address
+ 0,89% drm_do_probe_ddc_edid
+ 1,51% radeon_ddc_probe
+ 3,37% radeon_dp_detect
The program enumerates the VGA connectors with DRM_IOCTL_MODE_GETRESOURCES and
DRM_IOCTL_MODE_GETCONNECTOR syscalls. It's the first call to
DRM_IOCTL_MODE_GETCONNECTOR that seems to cause the issues on my system.
After I stop the program all is well again, the system is stable and I
experience no other issues.
When I ran the program on another system with a Radeon 5750 and a
recent kernel (4.5 or 4.6), it did not cause the intermittent freezes and
worked faster.
I'm running a dual DVI monitor setup and KDE 5. The issue also happens
under other window managers/DEs (IceWM, XFCE), so I don't think it is
related to KDE (but the pattern of connector lookups may have changed in a
recent Qt or xorg version so that the issue became more noticeable).
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