Kasper,
could you please try the "chew-max" latency-printing utility:
http://people.redhat.com/mingo/cfs-scheduler/tools/chew-max.c
if you start it on an idle system it prints a single line:
$ ./chew-max
pid 14506, prio 0, interval of 99984800 nsec
and prints nothing else. It continues looping and looping (using up 100%
of CPU time), and the moment it's preempted, it prints a line about that
preemption latency. Under higher load it will print something like this:
out for 63 ms [max: 66], ran for 5 ms, load 7
out for 85 ms [max: 85], ran for 4 ms, load 5
out for 7 ms [max: 85], ran for 0 ms, load 0
out for 105 ms [max: 105], ran for 3 ms, load 3
out for 174 ms [max: 174], ran for 6 ms, load 3
out for 219 ms [max: 219], ran for 3 ms, load 1
out for 78 ms [max: 219], ran for 3 ms, load 3
so that we get a picture of your latencies, could you run this tool why
you are seeing those 'bad' desktop latencies? (Since your CPU has two
cores it might make sense to run two instances of chew-max.)
record the latencies like this:
./chew-max > chew1.out &
./chew-max > chew2.out &
and send us the chew1.out and chew2.out files (bzip2 -9 compressed).
Thanks!
Ingo
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