Github user mateiz commented on a diff in the pull request:
https://github.com/apache/spark/pull/43#discussion_r10243564
--- Diff:
core/src/main/scala/org/apache/spark/storage/BlockFetcherIterator.scala ---
@@ -146,6 +146,12 @@ object BlockFetcherIterator {
}
protected def splitLocalRemoteBlocks(): ArrayBuffer[FetchRequest] = {
+ // Make remote requests at most maxBytesInFlight / 5 in length; the
reason to keep them
+ // smaller than maxBytesInFlight is to allow multiple, parallel
fetches from up to 5
+ // nodes, rather than blocking on reading output from one node.
+ val maxRequestSize = math.max(maxBytesInFlight / 5, 1L)
--- End diff --
Yeah I agree, note that the if statement below is `if (curRequestSize >=
maxRequestSize)`. In general you might have some requests bigger than this of
one map's output is just super large. This threshold is just used to batch
together small map outputs so we can grab more than one at once.
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