Symbolicate linux perf output of a node program using the v8 log

convert.js

var fs = require('fs');

var infile = process.argv[2];

if (!infile) return console.log("need infile");

var data = fs.readFileSync(infile, 'utf8').split('\n');
var outlines = [];

data.forEach(function(item) {
  var parts = item.split(',');

  if (parts.length < 5) return;
  if (parts[0] != 'code-creation') return;

  var length = parseInt(parts[3], 10).toString(16);
  var type = parts[1];
  var start = parts[2].slice(2);
  var name = parts[4].slice(1, -1);

  outlines.push(start + " " + length + " " + type + ":" + name);
});

console.log(outlines.join('\n'));

instructions.md

Use the v8 log to symbolicate linux perf output without having to upgrade yo node. This works with node v0.10. v0.11 has a slightly different v8 log file format so it won't quite work but a similar technique would work.

Run node like this

$ node --logfile="/tmp/node-%p.log" --nocompact_code_space --log_code program.js

Get some perf samples

$ perf record -e cycles:u -g -p $PID

Then convert the v8 log file to a perf map

$ node convert.js /tmp/node-$PID.log > /tmp/perf-$PID.map

Extract trace from perf.data file

$ perf script > perf-script.txt

And make a flame graph

cat perf-script.txt | flamegraph --inputtype perf > perf-graph.svg

The process works, but my flame graphs basically show two horizontal bars. Doesn't seem like anything of value is captured. Does this still work with node 0.10?