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jin xing commented on SPARK-19659: ---------------------------------- *bytesShuffleToMemory* is different from *bytesInFlight*. *bytesInFlight* is for only one *ShuffleBlockFetcherIterator* and get decreased when the remote blocks is received. *bytesShuffleToMemory* is for all ShuffleBlockFetcherIterators and get decreased only when reference count of ByteBuf is zero(though the memory maybe still inside cache and not really destroyed). If *spark.reducer.maxReqsInFlight* is only for memory control, I think *spark.reducer.maxBytesShuffleToMemory* is an improvement. In the current PR, I want to simplify the logic and the memory is tracked by *bytesShuffleToMemory* and memory usage is not tracked by MemoryManager. > Fetch big blocks to disk when shuffle-read > ------------------------------------------ > > Key: SPARK-19659 > URL: https://issues.apache.org/jira/browse/SPARK-19659 > Project: Spark > Issue Type: Improvement > Components: Shuffle > Affects Versions: 2.1.0 > Reporter: jin xing > Attachments: SPARK-19659-design-v1.pdf, SPARK-19659-design-v2.pdf > > > Currently the whole block is fetched into memory(offheap by default) when > shuffle-read. A block is defined by (shuffleId, mapId, reduceId). Thus it can > be large when skew situations. If OOM happens during shuffle read, job will > be killed and users will be notified to "Consider boosting > spark.yarn.executor.memoryOverhead". Adjusting parameter and allocating more > memory can resolve the OOM. However the approach is not perfectly suitable > for production environment, especially for data warehouse. > Using Spark SQL as data engine in warehouse, users hope to have a unified > parameter(e.g. memory) but less resource wasted(resource is allocated but not > used), > It's not always easy to predict skew situations, when happen, it make sense > to fetch remote blocks to disk for shuffle-read, rather than > kill the job because of OOM. This approach is mentioned during the discussion > in SPARK-3019, by [~sandyr] and [~mridulm80] -- This message was sent by Atlassian JIRA (v6.3.15#6346) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org