[
https://issues.apache.org/jira/browse/MAPREDUCE-4883?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13534505#comment-13534505
]
Lijie Xu commented on MAPREDUCE-4883:
-------------------------------------
[~tlipcon] Are there some other solutions? I think 2GB is a bit smaller for the
"large" reducer. Can we use 2D array to break this limit?
> 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
