To get flamecharts of iojs, use v8-profiler. v8-profiler's profiles, when JSONified, are in the .cpuprofile format the Chrome devtools' Profiler panel can load.

var profiler = require('v8-profiler');
profiler.startProfiling();
// work
var profile = profiler.stopProfiling();
var cpuprofileFormatted = JSON.stringify(profile, null, 2);
require('fs').writeFileSync('myprofile.cpuprofile', cpuprofileFormatted, 'utf8');
profile.delete();