From 4155741f7f486537d4a5f7193d79098d523a6ae8 Mon Sep 17 00:00:00 2001
From: Shay Banon <kimchy@gmail.com>
Date: Fri, 6 Sep 2013 02:25:17 +0200
Subject: [PATCH] BytesStreamOutput default size should be 2k instead of 32k We
 changed the default of BytesStreamOutput (used in various places in ES) to
 32k from 1k with the assumption that most stream tend to be large. This
 doesn't hold for example when indexing small documents and adding them using
 XContentBuilder (which will have a large overhead).

Default the buffer size to 2k now, but be relatively aggressive in expanding the buffer when below 256k (double it), and just use oversize (1/8th) when larger to try and minimize garbage and buffer copies.

relates to #3624
closes #3638
---
 .../common/io/stream/BytesStreamOutput.java   | 22 +++++++++++++++----
 .../common/io/streams/BytesStreamsTests.java  | 13 +++++++++++
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/src/main/java/org/elasticsearch/common/io/stream/BytesStreamOutput.java b/src/main/java/org/elasticsearch/common/io/stream/BytesStreamOutput.java
index 378a5fecb7a..52756377b5a 100644
--- a/src/main/java/org/elasticsearch/common/io/stream/BytesStreamOutput.java
+++ b/src/main/java/org/elasticsearch/common/io/stream/BytesStreamOutput.java
@@ -31,7 +31,9 @@ import java.io.IOException;
  */
 public class BytesStreamOutput extends StreamOutput implements BytesStream {
 
-    public static final int DEFAULT_SIZE = 32 * 1024;
+    public static final int DEFAULT_SIZE = 2 * 1024;
+
+    public static final int OVERSIZE_LIMIT = 256 * 1024;
 
     /**
      * The buffer where data is stored.
@@ -73,7 +75,7 @@ public class BytesStreamOutput extends StreamOutput implements BytesStream {
     public void writeByte(byte b) throws IOException {
         int newcount = count + 1;
         if (newcount > buf.length) {
-            buf = ArrayUtil.grow(buf, newcount);
+            buf = grow(newcount);
         }
         buf[count] = b;
         count = newcount;
@@ -82,7 +84,7 @@ public class BytesStreamOutput extends StreamOutput implements BytesStream {
     public void skip(int length) {
         int newcount = count + length;
         if (newcount > buf.length) {
-            buf = ArrayUtil.grow(buf, newcount);
+            buf = grow(newcount);
         }
         count = newcount;
     }
@@ -94,12 +96,20 @@ public class BytesStreamOutput extends StreamOutput implements BytesStream {
         }
         int newcount = count + length;
         if (newcount > buf.length) {
-            buf = ArrayUtil.grow(buf, newcount);
+            buf = grow(newcount);
         }
         System.arraycopy(b, offset, buf, count, length);
         count = newcount;
     }
 
+    private byte[] grow(int newCount) {
+        // try and grow faster while we are small...
+        if (newCount < OVERSIZE_LIMIT) {
+            newCount = Math.max(buf.length << 1, newCount);
+        }
+        return ArrayUtil.grow(buf, newCount);
+    }
+
     public void seek(int seekTo) {
         count = seekTo;
     }
@@ -108,6 +118,10 @@ public class BytesStreamOutput extends StreamOutput implements BytesStream {
         count = 0;
     }
 
+    public int bufferSize() {
+        return buf.length;
+    }
+
     @Override
     public void flush() throws IOException {
         // nothing to do there
diff --git a/src/test/java/org/elasticsearch/test/unit/common/io/streams/BytesStreamsTests.java b/src/test/java/org/elasticsearch/test/unit/common/io/streams/BytesStreamsTests.java
index c1f4dc450e3..d4ee4fff535 100644
--- a/src/test/java/org/elasticsearch/test/unit/common/io/streams/BytesStreamsTests.java
+++ b/src/test/java/org/elasticsearch/test/unit/common/io/streams/BytesStreamsTests.java
@@ -60,4 +60,17 @@ public class BytesStreamsTests {
         assertThat(in.readString(), equalTo("hello"));
         assertThat(in.readString(), equalTo("goodbye"));
     }
+
+    @Test
+    public void testGrowLogic() throws Exception {
+        BytesStreamOutput out = new BytesStreamOutput();
+        out.writeBytes(new byte[BytesStreamOutput.DEFAULT_SIZE - 5]);
+        assertThat(out.bufferSize(), equalTo(2048)); // remains the default
+        out.writeBytes(new byte[1 * 1024]);
+        assertThat(out.bufferSize(), equalTo(4608));
+        out.writeBytes(new byte[32 * 1024]);
+        assertThat(out.bufferSize(), equalTo(40320));
+        out.writeBytes(new byte[32 * 1024]);
+        assertThat(out.bufferSize(), equalTo(90720));
+    }
 }