[LITMUS^RT] high miss ratio for low task utilization

[jp walters]

Hi,

I'm just getting started with Litmus-RT, and I'm hoping someone can shed
some light on the results that I'm seeing.

I'm running the Litmus 2014.2 patch against the 3.10.41 upstream Linux
kernel.  I've built and installed the kernel according to the directions on
the wiki.

I've tested this on two systems with the same results.  The first is the
Ubuntu VM that's linked  on the wiki, mostly unmodified except for the
installing the development tools and updated kernel/liblitmus.  I allow the
VM 8GB RAM and 8 cores from a total of 128 physical cores on the machine.
The machine isn't loaded.  The second system is a non-virtualized 16 core
machine, also not loaded.

In both cases, everything builds fine, but when I try to sanity-check my
install using the experimental-scripts hosted on github, I'm finding that
the simple 3-task system generates some unexpected results.  I realize that
the experimental scripts on github aren't supported, but I'm hoping someone
can comment on whether the results I'm getting seem reasonable.

Using the run_exps.py script, everything looks reasonable, but when parsing
the results, I get the following:

root at ubuntu-qemu:~/experiment-scripts# ./parse_exps.py run-data/test1
Loading experiments...
Parsing data...
 0.00%
Writing csvs into parse-data...
Too little data to make csv files, printing results.
<ExpPoint-run-data/test1>
           block-avg:  Avg:     0.000  Max:     0.000  Min:     0.000  Var:
    0.000
           block-max:  Avg:     0.000  Max:     0.000  Min:     0.000  Var:
    0.000
          miss-ratio:  Avg:     1.000  Max:     1.000  Min:     1.000  Var:
    0.000
         record-loss:  Avg:     0.000  Max:     0.000  Min:     0.000  Var:
    0.000
            tard-avg:  Avg:     0.000  Max:     0.000  Min:     0.000  Var:
    0.000
            tard-max:  Avg:     0.000  Max:     0.000  Min:     0.000  Var:
    0.000

The 1.0 miss-ratio seems odd to me, given the resources available and the
workload described in the 3 tasks example.  Am I missing something?

best,
JP
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