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Signed-off-by: Pascal Spörri <psp@zurich.ibm.com>
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130 changes: 130 additions & 0 deletions
130
src/main/scala/org/apache/spark/storage/S3BufferedPrefetchIterator.scala
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,130 @@ | ||
| /** | ||
| * Copyright 2023- IBM Inc. All rights reserved | ||
| * SPDX-License-Identifier: Apache2.0 | ||
| */ | ||
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| package org.apache.spark.storage | ||
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| import org.apache.spark.internal.Logging | ||
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| import java.io.{BufferedInputStream, InputStream} | ||
| import java.util | ||
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| class S3BufferedPrefetchIterator(iter: Iterator[(BlockId, S3ShuffleBlockStream)], maxBufferSize: Long) extends Iterator[(BlockId, InputStream)] with Logging { | ||
| @volatile private var memoryUsage: Long = 0 | ||
| @volatile private var hasItem: Boolean = iter.hasNext | ||
| private var timeWaiting: Long = 0 | ||
| private var timePrefetching: Long = 0 | ||
| private var timeNext: Long = 0 | ||
| private var numStreams: Long = 0 | ||
| private var bytesRead: Long = 0 | ||
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| private var nextElement: (BlockId, S3ShuffleBlockStream) = null | ||
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| private val completed = new util.LinkedList[(InputStream, BlockId, Long)]() | ||
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| private def prefetchThread(): Unit = { | ||
| while (iter.hasNext || nextElement != null) { | ||
| if (nextElement == null) { | ||
| val now = System.nanoTime() | ||
| nextElement = iter.next() | ||
| timeNext = System.nanoTime() - now | ||
| } | ||
| val bsize = scala.math.min(maxBufferSize, nextElement._2.maxBytes).toInt | ||
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| var fetchNext = false | ||
| synchronized { | ||
| if (memoryUsage + math.min(bsize, maxBufferSize) > maxBufferSize) { | ||
| try { | ||
| wait() | ||
| } | ||
| catch { | ||
| case _: InterruptedException => | ||
| Thread.currentThread.interrupt() | ||
| } | ||
| } else { | ||
| fetchNext = true | ||
| } | ||
| } | ||
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| if (fetchNext) { | ||
| val block = nextElement._1 | ||
| val s = nextElement._2 | ||
| nextElement = null | ||
| val now = System.nanoTime() | ||
| val stream = new BufferedInputStream(s, bsize) | ||
| // Fill the buffered input stream by reading and then resetting the stream. | ||
| stream.mark(bsize) | ||
| stream.read() | ||
| stream.reset() | ||
| timePrefetching += System.nanoTime() - now | ||
| bytesRead += bsize | ||
| synchronized { | ||
| memoryUsage += bsize | ||
| completed.push((stream, block, bsize)) | ||
| hasItem = iter.hasNext | ||
| notifyAll() | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| private val self = this | ||
| private val thread = new Thread { | ||
| override def run(): Unit = { | ||
| self.prefetchThread() | ||
| } | ||
| } | ||
| thread.start() | ||
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| private def printStatistics(): Unit = synchronized { | ||
| try { | ||
| val tW = timeWaiting / 1000000 | ||
| val tP = timePrefetching / 1000000 | ||
| val tN = timeNext / 1000000 | ||
| val bR = bytesRead | ||
| val r = numStreams | ||
| // Average time per prefetch | ||
| val atP = tP / r | ||
| // Average time waiting | ||
| val atW = tW / r | ||
| // Average time next | ||
| val atN = tN / r | ||
| // Average read bandwidth | ||
| val bW = bR.toDouble / (tP.toDouble / 1000) / (1024 * 1024) | ||
| // Block size | ||
| val bs = bR / r | ||
| logInfo(s"Statistics: ${bR} bytes, ${tW} ms waiting (${atW} avg), " + | ||
| s"${tP} ms prefetching (avg: ${atP} ms - ${bs} block size - ${bW} MiB/s) " + | ||
| s"${tN} ms for next (${atN} avg)") | ||
| } catch { | ||
| case e: Exception => logError(f"Unable to print statistics: ${e.getMessage}.") | ||
| } | ||
| } | ||
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| override def hasNext: Boolean = synchronized { | ||
| val result = hasItem || (completed.size() > 0) | ||
| if (!result) { | ||
| printStatistics() | ||
| } | ||
| result | ||
| } | ||
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| override def next(): (BlockId, InputStream) = synchronized { | ||
| val now = System.nanoTime() | ||
| while (completed.isEmpty) { | ||
| try { | ||
| wait() | ||
| } catch { | ||
| case _: InterruptedException => | ||
| Thread.currentThread.interrupt() | ||
| } | ||
| } | ||
| timeWaiting += System.nanoTime() - now | ||
| numStreams += 1 | ||
| val result = completed.pop() | ||
| memoryUsage -= result._3 | ||
| notifyAll() | ||
| return (result._2, result._1) | ||
| } | ||
| } |
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