Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/15005#discussion_r78353504
--- Diff: docs/building-spark.md ---
@@ -16,24 +16,31 @@ Building Spark using Maven requires Maven 3.3.9 or
newer and Java 7+.
### Setting up Maven's Memory Usage
-You'll need to configure Maven to use more memory than usual by setting
`MAVEN_OPTS`. We recommend the following settings:
+If you are compiling with Java 7, you'll need to configure Maven to use
more memory than usual by setting `MAVEN_OPTS`:
export MAVEN_OPTS="-Xmx2g -XX:MaxPermSize=512M
-XX:ReservedCodeCacheSize=512m"
-If you don't run this, you may see errors like the following:
+When compiling with Java 8, a similar but smaller set of memory parameters
is necessary:
+
+ export MAVEN_OPTS="-Xmx2g -XX:ReservedCodeCacheSize=512m"
+
+If you don't add these parameters to `MAVEN_OPTS`, you may see errors like
the following:
[INFO] Compiling 203 Scala sources and 9 Java sources to
/Users/me/Development/spark/core/target/scala-{{site.SCALA_BINARY_VERSION}}/classes...
[ERROR] PermGen space -> [Help 1]
[INFO] Compiling 203 Scala sources and 9 Java sources to
/Users/me/Development/spark/core/target/scala-{{site.SCALA_BINARY_VERSION}}/classes...
[ERROR] Java heap space -> [Help 1]
-You can fix this by setting the `MAVEN_OPTS` variable as discussed before.
+You can fix these problems by setting the `MAVEN_OPTS` variable as
discussed before.
**Note:**
-* For Java 8 and above this step is not required.
-* If using `build/mvn` with no `MAVEN_OPTS` set, the script will automate
this for you.
+* This step is not needed for Java 8.
+* If using `build/mvn` with no `MAVEN_OPTS` set, the script will
automatically add the above options for Java 7 to the `MAVEN_OPTS` environment
variable.
+* The `test` phase of the Spark build will automatically add these options
to `MAVEN_OPTS`, even when not using `build/mvn`.
+* You may see warnings like "ignoring option MaxPermSize=1g; support was
removed in 8.0" when building or running tests with Java 8. These warnings are
harmless.
--- End diff --
If you follow these directions you won't see this warning; this could be
removed too.
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