[SPARK-9558][DOCS]Update docs to follow the increase of memory defaults.

Now the memory defaults of master and slave in Standalone mode and History Server is 1g, not 512m. So let's update docs.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #7896 from sarutak/update-doc-for-daemon-memory and squashes the following commits:

a77626c [Kousuke Saruta] Fix docs to follow the update of increase of memory defaults

conf/spark-env.sh.template

@@ -38,6 +38,7 @@
 # - SPARK_WORKER_INSTANCES, to set the number of worker processes per node
 # - SPARK_WORKER_DIR, to set the working directory of worker processes
 # - SPARK_WORKER_OPTS, to set config properties only for the worker (e.g. "-Dx=y")
+# - SPARK_DAEMON_MEMORY, to allocate to the master, worker and history server themselves (default: 1g).
 # - SPARK_HISTORY_OPTS, to set config properties only for the history server (e.g. "-Dx=y")
 # - SPARK_SHUFFLE_OPTS, to set config properties only for the external shuffle service (e.g. "-Dx=y")
 # - SPARK_DAEMON_JAVA_OPTS, to set config properties for all daemons (e.g. "-Dx=y")

docs/monitoring.md

@@ -48,7 +48,7 @@ follows:
   <tr><th style="width:21%">Environment Variable</th><th>Meaning</th></tr>
   <tr>
     <td><code>SPARK_DAEMON_MEMORY</code></td>
-    <td>Memory to allocate to the history server (default: 512m).</td>
+    <td>Memory to allocate to the history server (default: 1g).</td>
   </tr>
   <tr>
     <td><code>SPARK_DAEMON_JAVA_OPTS</code></td>

docs/spark-standalone.md

@@ -152,7 +152,7 @@ You can optionally configure the cluster further by setting environment variable
   </tr>
   <tr>
     <td><code>SPARK_DAEMON_MEMORY</code></td>
-    <td>Memory to allocate to the Spark master and worker daemons themselves (default: 512m).</td>
+    <td>Memory to allocate to the Spark master and worker daemons themselves (default: 1g).</td>
   </tr>
   <tr>
     <td><code>SPARK_DAEMON_JAVA_OPTS</code></td>