advancedxy commented on a change in pull request #26085: [SPARK-29434] [Core]
Improve the MapStatuses Serialization Performance
URL: https://github.com/apache/spark/pull/26085#discussion_r333810252
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File path: core/src/main/scala/org/apache/spark/MapOutputTracker.scala
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@@ -807,13 +808,17 @@ private[spark] object MapOutputTracker extends Logging {
private val BROADCAST = 1
// Serialize an array of map output locations into an efficient byte format
so that we can send
- // it to reduce tasks. We do this by compressing the serialized bytes using
GZIP. They will
+ // it to reduce tasks. We do this by compressing the serialized bytes using
Zstd. They will
// generally be pretty compressible because many map outputs will be on the
same hostname.
def serializeMapStatuses(statuses: Array[MapStatus], broadcastManager:
BroadcastManager,
isLocal: Boolean, minBroadcastSize: Int): (Array[Byte],
Broadcast[Array[Byte]]) = {
- val out = new ByteArrayOutputStream
- out.write(DIRECT)
- val objOut = new ObjectOutputStream(new GZIPOutputStream(out))
+ import scala.language.reflectiveCalls
+ val out = new ByteArrayOutputStream(4096) {
Review comment:
Just curious, is there any specific reason to choose 4096 here?
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