child_process: measure buffer length in bytes

This change fixes a known issue where `maxBuffer` limits by characters
rather than bytes. Benchmark added to confirm no performance regression
occurs with this change.

PR-URL: https://github.com/nodejs/node/pull/6764
Fixes: https://github.com/nodejs/node/issues/1901
Reviewed-By: Brian White <mscdex@mscdex.net>

2 files changed, 39 insertions, 9 deletions

diff --git a/benchmark/child_process/child-process-exec-stdout.js b/benchmark/child_process/child-process-exec-stdout.js
new file mode 100644
index 0000000000..79efb6fadf
--- /dev/null
+++ b/benchmark/child_process/child-process-exec-stdout.js
@@ -0,0 +1,30 @@
+'use strict';
+const common = require('../common.js');
+const bench = common.createBenchmark(main, {
+  len: [64, 256, 1024, 4096, 32768],
+  dur: [5]
+});
+
+const exec = require('child_process').exec;
+function main(conf) {
+  bench.start();
+
+  const dur = +conf.dur;
+  const len = +conf.len;
+
+  const msg = `"${'.'.repeat(len)}"`;
+  msg.match(/./);
+  const options = {'stdio': ['ignore', 'pipe', 'ignore']};
+  // NOTE: Command below assumes bash shell.
+  const child = exec(`while\n  echo ${msg}\ndo :; done\n`, options);
+
+  var bytes = 0;
+  child.stdout.on('data', function(msg) {
+    bytes += msg.length;
+  });
+
+  setTimeout(function() {
+    child.kill();
+    bench.end(bytes);
+  }, dur * 1000);
+}
diff --git a/benchmark/child_process/child-process-read.js b/benchmark/child_process/child-process-read.js
index c1a7474aae..33c268390f 100644
--- a/benchmark/child_process/child-process-read.js
+++ b/benchmark/child_process/child-process-read.js
@@ -1,20 +1,20 @@
 'use strict';
-var common = require('../common.js');
-var bench = common.createBenchmark(main, {
+const common = require('../common.js');
+const bench = common.createBenchmark(main, {
   len: [64, 256, 1024, 4096, 32768],
   dur: [5]
 });
 
-var spawn = require('child_process').spawn;
+const spawn = require('child_process').spawn;
 function main(conf) {
   bench.start();
 
-  var dur = +conf.dur;
-  var len = +conf.len;
+  const dur = +conf.dur;
+  const len = +conf.len;
 
-  var msg = '"' + Array(len).join('.') + '"';
-  var options = { 'stdio': ['ignore', 'ipc', 'ignore'] };
-  var child = spawn('yes', [msg], options);
+  const msg = '"' + Array(len).join('.') + '"';
+  const options = {'stdio': ['ignore', 'ipc', 'ignore']};
+  const child = spawn('yes', [msg], options);
 
   var bytes = 0;
   child.on('message', function(msg) {
@@ -23,7 +23,7 @@ function main(conf) {
 
   setTimeout(function() {
     child.kill();
-    var gbits = (bytes * 8) / (1024 * 1024 * 1024);
+    const gbits = (bytes * 8) / (1024 * 1024 * 1024);
     bench.end(gbits);
   }, dur * 1000);
 }