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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - RT cpu starvation due to driver threads or memory access"
href="https://bugs.freedesktop.org/show_bug.cgi?id=110950#c6">Comment # 6</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - RT cpu starvation due to driver threads or memory access"
href="https://bugs.freedesktop.org/show_bug.cgi?id=110950">bug 110950</a>
from <span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span></b>
<pre>Just a quick check on the baseline, the results of our cycletest for measuring
RT thread latency, maximum latency measured during a 120s period:
x baseline-max.lt
+ i915-max.lt
+------------------------------------------------------------------------------+
| xxx +
|
| xxxxx + + +
|
| xxxxx ++ + *
|
| xxxxxx *+ + *
|
| xxxxxxx *+ ++*
|
| xxxxxxx x*+ ++*
|
| xxxxxxx **+x*+*
|
|xxxxxxxxx **+*****+ + + + + + + +
|
|xxxxxxxxxx**+*****+x+ + ++ + + + ++ + + ++ ++ + + + +
|
|xxxxxxxxxx**+******x**x*x++++*+ ++ + ++ ++++ + ++ ++ ++++ +++++++++ +
++|
| |____M_A_____|
|
| |___________M_________A____________________|
|
+------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 120 11 47 18 20.533333 7.7924045
+ 120 23 105 39 50.716667 26.207377
in microseconds. So even in the best case, the worst case impact of submitting
nops is on average 50us.
Now, this does not take into account any impact memory contention has on the RT
thread since we are not stressing the GPU in that manner. Nor does it setup an
isolated cpu. Just establishing expectations for j1900.</pre>
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