8011135: (bf) CharBuffer.put(String) is slow because of String.charAt() call for each char

[Brian Burkhalter]

https://bugs.openjdk.java.net/browse/JDK-8011135 <https://bugs.openjdk.java.net/browse/JDK-8011135>

With the proposed change [1] applied, the performance of CharBuffer.put(String) was measured [2] to be 5-6X faster than without the change [3].

Thanks,

Brian

[1] diff

--- a/src/java.base/share/classes/java/nio/Heap-X-Buffer.java.template
+++ b/src/java.base/share/classes/java/nio/Heap-X-Buffer.java.template
@@ -270,6 +270,22 @@
 #end[rw]
     }
 
+#if[char]
+
+    public $Type$Buffer put(String src, int start, int end) {
+        int length = end - start;
+        checkBounds(start, length, src.length());
+        if (isReadOnly())
+            throw new ReadOnlyBufferException();
+        if (length > remaining())
+            throw new BufferOverflowException();
+        src.getChars(start, end, hb, ix(position()));
+        position(position() + length);
+        return this;
+    }
+
+#end[char]
+
     public $Type$Buffer compact() {


[2] benchmark

public class PutStringBench {

    private static final String STR = new String
        (" abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 ");

    private static final CharBuffer BUF = CharBuffer.allocate(1024);

    @Benchmark
    public CharBuffer putString() {
        BUF.rewind();
        return BUF.put(STR);
    }

}


[3] results
[a] before

Result "com.oracle.PutStringBench.putString":
  18764158.739 ±(99.9%) 250376.712 ops/s [Average]
  (min, avg, max) = (18614233.510, 18764158.739, 19122478.453), stdev = 165608.693
  CI (99.9%): [18513782.027, 19014535.452] (assumes normal distribution)

Result "com.oracle.PutStringBench.putString":
  15920473.709 ±(99.9%) 1212446.652 ops/s [Average]
  (min, avg, max) = (14842084.221, 15920473.709, 17371424.249), stdev = 801958.390
  CI (99.9%): [14708027.056, 17132920.361] (assumes normal distribution)

Benchmark                  Mode  Cnt         Score        Error  Units
PutStringBench.putString  thrpt    5  18571082.538 ± 693010.965  ops/s

[b] after

Result "com.oracle.PutStringBench.putString":
  108696688.710 ±(99.9%) 3774080.561 ops/s [Average]
  (min, avg, max) = (101907400.750, 108696688.710, 110524934.117), stdev = 2496320.615
  CI (99.9%): [104922608.149, 112470769.272] (assumes normal distribution)

Result "com.oracle.PutStringBench.putString":
  103110531.621 ±(99.9%) 5281599.715 ops/s [Average]
  (min, avg, max) = (96691960.810, 103110531.621, 106781180.294), stdev = 3493451.195
  CI (99.9%): [97828931.906, 108392131.336] (assumes normal distribution)

Benchmark                  Mode  Cnt          Score         Error  Units
PutStringBench.putString  thrpt    5  106026596.397 ± 1375553.439  ops/s

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.java.net/pipermail/nio-dev/attachments/20190220/780d65c5/attachment.html>