Documentation update for compression codec.

docs/configuration.md

@@ -35,7 +35,7 @@ for these variables.
 * `SPARK_JAVA_OPTS`, to add JVM options. This includes any system properties that you'd like to pass with `-D`.
 * `SPARK_CLASSPATH`, to add elements to Spark's classpath.
 * `SPARK_LIBRARY_PATH`, to add search directories for native libraries.
-* `SPARK_MEM`, to set the amount of memory used per node. This should be in the same format as the 
+* `SPARK_MEM`, to set the amount of memory used per node. This should be in the same format as the
    JVM's -Xmx option, e.g. `300m` or `1g`. Note that this option will soon be deprecated in favor of
    the `spark.executor.memory` system property, so we recommend using that in new code.
 
@@ -77,7 +77,7 @@ there are at least five properties that you will commonly want to control:
     Class to use for serializing objects that will be sent over the network or need to be cached
     in serialized form. The default of Java serialization works with any Serializable Java object but is
     quite slow, so we recommend <a href="tuning.html">using <code>spark.KryoSerializer</code>
-    and configuring Kryo serialization</a> when speed is necessary. Can be any subclass of 
+    and configuring Kryo serialization</a> when speed is necessary. Can be any subclass of
     <a href="api/core/index.html#spark.Serializer"><code>spark.Serializer</code></a>).
   </td>
 </tr>
@@ -86,7 +86,7 @@ there are at least five properties that you will commonly want to control:
   <td>(none)</td>
   <td>
     If you use Kryo serialization, set this class to register your custom classes with Kryo.
-    You need to set it to a class that extends 
+    You need to set it to a class that extends
     <a href="api/core/index.html#spark.KryoRegistrator"><code>spark.KryoRegistrator</code></a>).
     See the <a href="tuning.html#data-serialization">tuning guide</a> for more details.
   </td>
@@ -180,6 +180,21 @@ Apart from these, the following properties are also available, and may be useful
     Can save substantial space at the cost of some extra CPU time.
   </td>
 </tr>
+<tr>
+  <td>spark.io.compression.codec</td>
+  <td>spark.io.SnappyCompressionCodec</td>
+  <td>
+    The compression codec class to use for various compressions. By default, Spark provides two
+    codecs: <code>spark.io.LZFCompressionCodec</code> and <code>spark.io.SnappyCompressionCodec</code>.
+  </td>
+</tr>
+<tr>
+  <td>spark.io.compression.snappy.block.size</td>
+  <td>32768</td>
+  <td>
+    Block size (in bytes) used in Snappy compression, in the case when Snappy compression codec is used.
+  </td>
+</tr>
 <tr>
   <td>spark.reducer.maxMbInFlight</td>
   <td>48</td>