ustat: Add man page and companion example file
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+Demonstrations of ustat.
+
+
+ustat is a "top"-like tool for monitoring events in high-level languages. It
+prints statistics about garbage collections, method calls, object allocations,
+and various other events for every process that it recognizes with a Java,
+Python, Ruby, or Node runtime.
+
+For example:
+
+# ./ustat.py
+Tracing... Output every 10 secs. Hit Ctrl-C to end
+12:17:17 loadavg: 0.33 0.08 0.02 5/211 26284
+
+PID CMDLINE METHOD/s GC/s OBJNEW/s CLOAD/s EXC/s THR/s
+3018 node/node 0 3 0 0 0 0
+^C
+Detaching...
+
+
+If desired, you can instruct ustat to print a certain number of entries and
+exit, which can be useful to get a quick picture on what's happening on the
+system over a short time interval. Here, we ask ustat to print 5-second
+summaries 12 times (for a total time of 1 minute):
+
+# ./ustat.py -C 5 12
+Tracing... Output every 5 secs. Hit Ctrl-C to end
+12:18:26 loadavg: 0.27 0.11 0.04 2/336 26455
+
+PID CMDLINE METHOD/s GC/s OBJNEW/s CLOAD/s EXC/s THR/s
+3018 node/node 0 1 0 0 0 0
+
+12:18:31 loadavg: 0.33 0.12 0.04 2/336 26456
+
+PID CMDLINE METHOD/s GC/s OBJNEW/s CLOAD/s EXC/s THR/s
+3018 node/node 0 0 0 0 0 0
+26439 java -XX:+ExtendedDT 2776045 0 0 0 0 0
+
+12:18:37 loadavg: 0.38 0.14 0.05 2/336 26457
+
+PID CMDLINE METHOD/s GC/s OBJNEW/s CLOAD/s EXC/s THR/s
+3018 node/node 0 0 0 0 0 0
+26439 java -XX:+ExtendedDT 2804378 0 0 0 0 0
+
+(...more output omitted for brevity)
+
+
+USAGE message:
+
+# ./ustat.py -h
+usage: ustat.py [-h] [-l {java,python,ruby,node}] [-C]
+ [-S {cload,excp,gc,method,objnew,thread}] [-r MAXROWS] [-d]
+ [interval] [count]
+
+Activity stats from high-level languages.
+
+positional arguments:
+ interval output interval, in seconds
+ count number of outputs
+
+optional arguments:
+ -h, --help show this help message and exit
+ -l {java,python,ruby,node}, --language {java,python,ruby,node}
+ language to trace (default: all languages)
+ -C, --noclear don't clear the screen
+ -S {cload,excp,gc,method,objnew,thread}, --sort {cload,excp,gc,method,objnew,thread}
+ sort by this field (descending order)
+ -r MAXROWS, --maxrows MAXROWS
+ maximum rows to print, default 20
+ -d, --debug Print the resulting BPF program (for debugging
+ purposes)
+
+examples:
+ ./ustat # stats for all languages, 1 second refresh
+ ./ustat -C # don't clear the screen
+ ./ustat -l java # Java processes only
+ ./ustat 5 # 5 second summaries
+ ./ustat 5 10 # 5 second summaries, 10 times only