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https://issues.apache.org/jira/browse/SPARK-15391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15300529#comment-15300529
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Reynold Xin commented on SPARK-15391:
-------------------------------------
We should look into this -- do proper memory management for timsort buffers.
If it ends up being too difficult, we can also switch to quicksort since most
quicksort implementations can sort in place. However, based on our testing,
quicksort is often slower.
> Spark executor OOM during TimSort
> ---------------------------------
>
> Key: SPARK-15391
> URL: https://issues.apache.org/jira/browse/SPARK-15391
> Project: Spark
> Issue Type: Bug
> Reporter: Sital Kedia
>
> While running a query, we are seeing a lot of executor OOM while doing
> TimSort.
> Stack trace -
> {code}
> at
> org.apache.spark.util.collection.unsafe.sort.UnsafeSortDataFormat.allocate(UnsafeSortDataFormat.java:86)
> at
> org.apache.spark.util.collection.unsafe.sort.UnsafeSortDataFormat.allocate(UnsafeSortDataFormat.java:32)
> at
> org.apache.spark.util.collection.TimSort$SortState.ensureCapacity(TimSort.java:951)
> at
> org.apache.spark.util.collection.TimSort$SortState.mergeLo(TimSort.java:699)
> at
> org.apache.spark.util.collection.TimSort$SortState.mergeAt(TimSort.java:525)
> at
> org.apache.spark.util.collection.TimSort$SortState.mergeCollapse(TimSort.java:453)
> at
> org.apache.spark.util.collection.TimSort$SortState.access$200(TimSort.java:325)
> at org.apache.spark.util.collection.TimSort.sort(TimSort.java:153)
> at org.apache.spark.util.collection.Sorter.sort(Sorter.scala:37)
> at
> org.apache.spark.util.collection.unsafe.sort.UnsafeInMemorySorter.getSortedIterator(UnsafeInMemorySorter.java:235)
> at
> org.apache.spark.util.collection.unsafe.sort.UnsafeExternalSorter.spill(UnsafeExternalSorter.java:198)
> at org.apache.spark.memory.MemoryConsumer.spill(MemoryConsumer.java:58)
> at
> org.apache.spark.util.collection.unsafe.sort.UnsafeExternalSorter.insertRecord(UnsafeExternalSorter.java:356)
> at
> org.apache.spark.sql.execution.UnsafeExternalRowSorter.insertRow(UnsafeExternalRowSorter.java:91)
> {code}
> Out of total 32g available to the executors, we are allocating 24g onheap and
> 8g onheap memory. Looking at the code
> (https://github.com/apache/spark/blob/master/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeSortDataFormat.java#L87),
> we see that during TimSort we are allocating the memory buffer onheap
> irrespective of memory mode that is reason of executor OOM.
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