[Bug 39202] FPS - KDE desktop effects with 3.0 rc6 kernel

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=39202

--- Comment #36 from Ilija Hadzic <ihadzic at research.bell-labs.com> 2011-08-18 10:32:41 PDT ---
(In reply to comment #34)
> (In reply to comment #33)
> 
> I booted into kde 4.7.0 with a 3.1.0-rc2 kernel and then I did:
> echo 7 > /sys/module/drm/parameters/debug
> and then I launched glxgears (and didn't close it).
> Then I did:
> dmesg | grep waiting
> [  329.830313] [drm:drm_wait_vblank], waiting on vblank count 19676, crtc 0
> [  329.834052] [drm:drm_wait_vblank], waiting on vblank count 19677, crtc 0
> [  329.834068] [drm:drm_wait_vblank], waiting on vblank count 19677, crtc 0
> 
> ----------------- [SNIP]-----------------------------
>
> Everything seems to be crtc 0 (and I have only the vga cable connected to the 
> monitor vga output).
> 
> I have Pageflipping off, SwapBuffersWait off.

CRTC0 (routed to the connected connector) is correct when only one cable is
connected. Does the frame rate reported by glxgears match your monitor refresh
rate ? ... 60 ? If so then this is correct and that *should* be the value
reported by KDE as well when you turn on desktop effects. Is it ? (turn 
SwapBuffersWait and PageFlipping back on). If that's also 60 (exactly 60 and
equal to your monitor refresh rate, *not* lower) then your system is behaving 
as it should and anything you saw differently before was wrong.

If it's lower than 60, then the only thing I can think of is that something
slows down your system so much that it can't complete whatever it needs to do
between two buffer swap requests and is actually missing vblanks. Following
that logic, the explanation for 100 you saw in the old kernel would be
that it wasn't synchronizing at all and 100 was the top speed it could do
in a tight loop without any waiting. That's also consistent with what
you said in your next post, that you don't see the "waiting on vblank"
messages from the kernel.

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