Improve parallelism

Author: ehmicky

src/stream.js

@@ -12,13 +12,16 @@ const { getError } = require('./error')
 // call to those functions would be more efficient that creating lots of
 // child processes through streaming.
 const execStream = function(mapFunc, opts) {
-  const optsA = { ...DEFAULT_OPTS, ...opts }
+  const { maxConcurrency, ...optsA } = { ...DEFAULT_OPTS, ...opts }
 
   // `maxConcurrency` `through2` option is not specified because `gulp.src()`
   // always has a `highWaterMark` of `16` meaning only 16 files are processed
   // at a time in parallel. `maxConcurrency` can then only be used to decrease
   // that level of parallelism but `16` is already quite low.
-  return through.obj(execVinyl.bind(null, { mapFunc, opts: optsA }))
+  return through.obj(
+    { maxConcurrency },
+    execVinyl.bind(null, { mapFunc, opts: optsA }),
+  )
 }
 
 const DEFAULT_OPTS = {
@@ -29,6 +32,8 @@ const DEFAULT_OPTS = {
   stderr: 'pipe',
   // Prevents echoing by default because it would be done on each iteration.
   echo: false,
+  // The default is 16 which is too low
+  maxConcurrency: 100,
 }
 
 // eslint-disable-next-line max-params, promise/prefer-await-to-callbacks