Useful scripts to collect/display perf results.

Add shell scripts to make it easier to collect performance results from
traces, live tests, and phoronix tests.

With run_performance_tests.sh you specify the following:
  - a subject program to run, using --root
  - a name to give to this set of results, using --variant
  - a test to run, using --test
  - a file to write the results to, using --results.

For tests that start with "trace", the script runs falco/sysdig on the
trace file and measures the time taken to read the file. For other
tests, he script handles starting falco/sysdig, starting a cpu
measurement script (a wrapper around top, just to provide identical
values to what you would see using top) to measure the cpu usage of
falco/sysdig, and running a live test.

The measurement interval for cpu usage depends on the test being run--10
seconds for most tests, 2 seconds for shorter tests.

The output is written as json to the file specified in --results.

Also add R scripts to easily display the results from the shell
script. plot-live.r shows a linechart of the cpu usage for the provided
variants over time. plot-traces.r shows grouped barcharts showing
user/system/total time taken for the provided variants and traces.

One bug--you have to make the results file actual json by adding
leading/trailing []s.

test/cpu_monitor.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+SUBJ_PID=$1
+BENCHMARK=$2
+VARIANT=$3
+RESULTS_FILE=$4
+CPU_INTERVAL=$5
+
+top -d $CPU_INTERVAL -b -p $SUBJ_PID | grep -E '(falco|sysdig)' --line-buffered | awk -v benchmark=$BENCHMARK -v variant=$VARIANT '{printf("{\"sample\": %d, \"benchmark\": \"%s\", \"variant\": \"%s\", \"cpu_usage\": %s},\n", NR, benchmark, variant, $9); fflush();}' >> $RESULTS_FILE