lib/bench.js
function runSync () {
    for (runIndex = 0; runIndex < sampleSize; runIndex++) {
      fn.call(child)
    }
    setTimeout(finishChild, 0)
  }
function runSync () {
    for (runIndex = 0; runIndex < sampleSize; runIndex++) {
      fn.call(child)
    }
    setTimeout(finishChild, 0)
  }
Run the current child's test function synchronously.