[SPARK-50996][K8S] Increase spark.kubernetes.allocation.batch.size to 10

docs/core-migration-guide.md

@@ -36,6 +36,8 @@ license: |
 
 - In Spark 4.0, support for Apache Mesos as a resource manager was removed.
 
+- Since Spark 4.0, Spark will allocate executor pods with a batch size of `10`. To restore the legacy behavior, you can set `spark.kubernetes.allocation.batch.size` to `5`.
+
 - Since Spark 4.0, Spark uses `ReadWriteOncePod` instead of `ReadWriteOnce` access mode in persistence volume claims. To restore the legacy behavior, you can set `spark.kubernetes.legacy.useReadWriteOnceAccessMode` to `true`.
 
 - Since Spark 4.0, Spark reports its executor pod status by checking all containers of that pod. To restore the legacy behavior, you can set `spark.kubernetes.executor.checkAllContainers` to `false`.

docs/running-on-kubernetes.md

@@ -682,7 +682,7 @@ See the [configuration page](configuration.html) for information on Spark config
 </tr>
 <tr>
   <td><code>spark.kubernetes.allocation.batch.size</code></td>
-  <td><code>5</code></td>
+  <td><code>10</code></td>
   <td>
     Number of pods to launch at once in each round of executor pod allocation.
   </td>

resource-managers/kubernetes/core/src/main/scala/org/apache/spark/deploy/k8s/Config.scala

@@ -450,7 +450,7 @@ private[spark] object Config extends Logging {
       .version("2.3.0")
       .intConf
       .checkValue(value => value > 0, "Allocation batch size should be a positive integer")
-      .createWithDefault(5)
+      .createWithDefault(10)
 
   val KUBERNETES_ALLOCATION_BATCH_DELAY =
     ConfigBuilder("spark.kubernetes.allocation.batch.delay")