http://bugzilla.kernel.org/show_bug.cgi?id=13713
Summary: [drm/i915] Possible regression due to commit "Change
GEM throttling to be 20ms (...)"
Product: Drivers
Version: 2.5
Kernel Version: 2.6.31-rc2
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Video(DRI)
AssignedTo: [email protected]
ReportedBy: [email protected]
Regression: Yes
Some low demanding 3D accelerated applications (tested: quake3-demo, glxgears,
stepmania 3.9) seem to suffer from a starvation of some sort. They are unusable
and temporarily freeze the X itself.
The applications render their frames in bursts - a few frames show up, then it
freezes for a split of a second (X itself too). The bursts occur quite
regularly, a few times per second. In quake3-demo while cg_drawfps was enabled,
the frame rate would burst between numbers like 50 and 300.
Reverting the commit b962442e46a9340bdbc6711982c59ff0cc2b5afb - "drm/i915:
Change GEM throttling to be 20ms like the comment says." fixes the issue for
me.
Also, limiting maximum frame rate (com_maxfps) in quake3-demo to about ~50
(1000ms / 20 ms = 50 -- I thought) eliminates the bursts. The greater the limit
the stronger the bursts are. Enabling vertical sync seems to help too (as I
have 60hz).
I tested against mesa/xorg-server/xf86-video-intel from git, and latest
official releases. This happens on all three combination: EXA/UXA/UXA+KMS and
regardless of Tiling option.
My laptop: Intel GM965/GL960, 1GB of ram, Intel Core 2 Duo T7100 @ 1.80GHz.
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