Cap the number of FDs used by barback at 32.

pkg/barback/lib/src/file_pool.dart

Index: pkg/barback/lib/src/file_pool.dart
diff --git a/pkg/barback/lib/src/file_pool.dart b/pkg/barback/lib/src/file_pool.dart
index 64aa404e10b3fc8ec04f1147c129a955b7b615a7..89e3e80ea24c172159cc1e3f92336acd516986c0 100644
--- a/pkg/barback/lib/src/file_pool.dart
+++ b/pkg/barback/lib/src/file_pool.dart
@@ -38,8 +38,9 @@ class FilePool {
 
   /// The maximum number of file descriptors that the pool will allocate.
   ///
-  /// Barback may only use half the available file descriptors.
-  int get _maxOpenFiles => (maxFileDescriptors / 2).floor();
+  /// This is based on empirical tests that indicate that beyond 32, additional
+  /// file reads don't provide substantial additional throughput.
+  final int _maxOpenFiles = 32;

[dgrove, 2013/10/22 20:31:48]

Did you try measuring this on a variety of computers? This number seems pretty
low - if this is the case across powerful machines, can you please file a bug
with dart:io?

 
   /// Opens [file] for reading.
   ///