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Todd Lipcon commented on MAPREDUCE-4883: ---------------------------------------- I believe, even in a 64-bit JVM, the max array size is Integer.MAX_VALUE (2GB) > Reducer's Maximum Shuffle Buffer Size should be enlarged for 64bit JVM > ---------------------------------------------------------------------- > > Key: MAPREDUCE-4883 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-4883 > Project: Hadoop Map/Reduce > Issue Type: Improvement > Affects Versions: 0.20.2, 1.0.3 > Environment: Especially for 64bit JVM > Reporter: Lijie Xu > Labels: patch > Original Estimate: 12h > Remaining Estimate: 12h > > In hadoop-0.20.2, hadoop-1.0.3 or other versions, reducer's shuffle buffer > size cannot exceed 2048MB (i.e., Integer.MAX_VALUE). This is reasonable for > 32bit JVM. > But for 64bit JVM, although reducer's JVM size can be set more than 2048MB > (e.g., mapred.child.java.opts=-Xmx4000m), the heap size used for shuffle > buffer is at most "2048MB * maxInMemCopyUse (default 0.7)" not "4000MB * > maxInMemCopyUse". > So the pointed piece of code in ReduceTask.java needs modification for 64bit > JVM. > --------------------------------------------------------------------------------------- > private final long maxSize; > private final long maxSingleShuffleLimit; > > private long size = 0; > > private Object dataAvailable = new Object(); > private long fullSize = 0; > private int numPendingRequests = 0; > private int numRequiredMapOutputs = 0; > private int numClosed = 0; > private boolean closed = false; > > public ShuffleRamManager(Configuration conf) throws IOException { > final float maxInMemCopyUse = > conf.getFloat("mapred.job.shuffle.input.buffer.percent", 0.70f); > if (maxInMemCopyUse > 1.0 || maxInMemCopyUse < 0.0) { > throw new IOException("mapred.job.shuffle.input.buffer.percent" + > maxInMemCopyUse); > } > // Allow unit tests to fix Runtime memory > --> maxSize = (int)(conf.getInt("mapred.job.reduce.total.mem.bytes", > --> (int)Math.min(Runtime.getRuntime().maxMemory(), Integer.MAX_VALUE)) > --> * maxInMemCopyUse); > maxSingleShuffleLimit = (long)(maxSize * > MAX_SINGLE_SHUFFLE_SEGMENT_FRACTION); > LOG.info("ShuffleRamManager: MemoryLimit=" + maxSize + > ", MaxSingleShuffleLimit=" + maxSingleShuffleLimit); > } -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira