Github user zsxwing commented on a diff in the pull request:
https://github.com/apache/spark/pull/5868#discussion_r30093113
--- Diff:
core/src/main/scala/org/apache/spark/shuffle/unsafe/UnsafeShuffleManager.scala
---
@@ -0,0 +1,178 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.shuffle.unsafe
+
+import org.apache.spark._
+import org.apache.spark.serializer.Serializer
+import org.apache.spark.shuffle._
+import org.apache.spark.shuffle.sort.SortShuffleManager
+
+/**
+ * Subclass of [[BaseShuffleHandle]], used to identify when we've chosen
to use the new shuffle.
+ */
+private class UnsafeShuffleHandle[K, V](
+ shuffleId: Int,
+ override val numMaps: Int,
+ override val dependency: ShuffleDependency[K, V, V])
+ extends BaseShuffleHandle(shuffleId, numMaps, dependency) {
+}
+
+private[spark] object UnsafeShuffleManager extends Logging {
+ /**
+ * Helper method for determining whether a shuffle should use the
optimized unsafe shuffle
+ * path or whether it should fall back to the original sort-based
shuffle.
+ */
+ def canUseUnsafeShuffle[K, V, C](dependency: ShuffleDependency[K, V,
C]): Boolean = {
+ val shufId = dependency.shuffleId
+ val serializer = Serializer.getSerializer(dependency.serializer)
+ if (!serializer.supportsRelocationOfSerializedObjects) {
+ log.debug(s"Can't use UnsafeShuffle for shuffle $shufId because the
serializer, " +
--- End diff --
I propose to use `log.warn` here. It would be much easier for people to
compare the performances of `UnsafeShuffleManager ` and `SortShuffleManager`.
They usually need to know the new `UnsafeShuffleHandle` does take effect.
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