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Sean Owen commented on SPARK-17951: ----------------------------------- I'm not sure this suggests a problem with Spark. It's a very small difference in absolute terms and may say more about the benchmark than Spark. It's also an internal API. Do you have a bigger difference in calls to a user-facing API? > BlockFetch with multiple threads slows down after spark 1.6 > ----------------------------------------------------------- > > Key: SPARK-17951 > URL: https://issues.apache.org/jira/browse/SPARK-17951 > Project: Spark > Issue Type: Bug > Components: Block Manager, Spark Core > Affects Versions: 1.6.2 > Environment: cluster with 8 node, each node has 28 cores. 10Gb network > Reporter: ding > > The following code demonstrates the issue: > {code} > def main(args: Array[String]): Unit = { > val conf = new SparkConf().setAppName(s"BMTest") > val size = 3344570 > val sc = new SparkContext(conf) > val data = sc.parallelize(1 to 100, 8) > var accum = sc.accumulator(0.0, "get remote bytes") > var i = 0 > while(i < 91) { > accum = sc.accumulator(0.0, "get remote bytes") > val test = data.mapPartitionsWithIndex { (pid, iter) => > val N = size > val bm = SparkEnv.get.blockManager > val blockId = TaskResultBlockId(10*i + pid) > val test = new Array[Byte](N) > Random.nextBytes(test) > val buffer = ByteBuffer.allocate(N) > buffer.limit(N) > buffer.put(test) > bm.putBytes(blockId, buffer, StorageLevel.MEMORY_ONLY_SER) > Iterator(1) > }.count() > > data.mapPartitionsWithIndex { (pid, iter) => > val before = System.nanoTime() > > val bm = SparkEnv.get.blockManager > (0 to 7).map(s => { > Future { > val result = bm.getRemoteBytes(TaskResultBlockId(10*i + s)) > } > }).map(Await.result(_, Duration.Inf)) > > accum.add((System.nanoTime() - before) / 1e9) > Iterator(1) > }.count() > println("get remote bytes take: " + accum.value/8) > i += 1 > } > } > {code} > In spark1.6.2, average of "getting remote bytes" time is: 0.19 s while > in spark 1.5.1 average of "getting remote bytes" time is: 0.09 s > However if fetch block in single thread, the gap is much smaller. > spark1.6.2 get remote bytes: 0.21 s > spark1.5.1 get remote bytes: 0.20 s -- This message was sent by Atlassian JIRA (v6.3.4#6332) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org