i think if you are relatively sure that the box does not have any real
3D hardware in it (supported by X) then glxgears will interact badly
with X and can cause such symptoms. In that case glxgears 'spams' the X
server with requests and everyone else suffers from that. The fair-group
scheduler indeed could shift CPU usage of X just enough (in X's favor!)
that might trigger such problems. Such "spam X" workloads often react in
a paradoxial way: a scheduler that gives X _more_ CPU time will appear
to be "less interactive".)
Ingo
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