New KTR trace for mouse freezing/stuttering in 7.0-RC1

Joe Peterson joe at
Wed Jan 23 21:10:28 PST 2008

In an attempt to track down this mouse freezing/stuttering (i.e. "jerky
mouse movement) behavior in FreeBSD 7.0-RC1, I have come up with a
reliable way to cause it to happen, and I have created a longer trace
showing the results.  Note that I am using the ULE scheduler.

In general, it becomes easier to see the effect if there is CPU
activity.  I have noticed it during kernel compiles, while at the same
time loading web pages in firefox that contain images (and moving the
mouse while this is happening).  But a more controlled way to see it is
to run something that uses some CPU and then generating lots of X events.

In my case, I start "xtrs" (TRS-80 emulator) in Model IV mode, which
happens to poll for input, using the CPU.  Then I move the mouse back
and forth quickly between windows in "focus under mouse" mode (in my
case, a KDE focus mode), which causes many focus events quickly.  In
about 15 or 20 seconds, the mouse reliably starts to show erratic
movement, not moving smoothly.

I really hope this can shed more light on what might be going on.  Here
is the trace:

					Thanks, Joe

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