[GitHub] [spark] amuraru commented on a change in pull request #23695: [SPARK-26780][CORE]Improve shuffle read using ReadAheadInputStream

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amuraru commented on a change in pull request #23695: [SPARK-26780][CORE]Improve shuffle read using ReadAheadInputStream 
URL: https://github.com/apache/spark/pull/23695#discussion_r280085711
 
 

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 File path: core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
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 @@ -474,6 +475,12 @@ final class ShuffleBlockFetcherIterator(
               // TODO: manage the memory used here, and spill it into disk in case of OOM.
               Utils.copyStream(input, out, closeStreams = true)
               input = out.toChunkedByteBuffer.toInputStream(dispose = true)
+            } else {
+              val readAheadEnabled = SparkEnv.get != null &&
+                SparkEnv.get.conf.get(config.SHUFFLE_READ_AHEAD)
+              if (readAheadEnabled) {
+                input = new ReadAheadInputStream(input, 1024 * 1024)
 
 Review comment:
   IIUC this won't be enabled when `detectCorruptUseExtraMemory` is set.
   Would it make sense to document this?

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