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https://issues.apache.org/jira/browse/HIVE-15565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15824756#comment-15824756
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Rajesh Balamohan commented on HIVE-15565:
-----------------------------------------
As per old impl, maxMemory in {{GroupByOperator}} was 5,312,784,896. After
running few queries (e.g q22,18, 70, 67) heap usage increases to ~64GB. Now
when q22 is rerun, {{GroupByOperator::shouldBeFlushed}} would always return
true for every record due to the following calculation
{noformat}
usedMemory = isLlap ? usedMemory / numExecutors : usedMemory;
rate = (float) usedMemory / (float) maxMemory; <==== 64/12 = 5.33 GB /
5312784896 bytes > memoryThreshold of 0.9.
if(rate > memoryThreshold){
return true;
}
{noformat}
Even though q22 dataset is very small, it would end up flushing for every row.
Patch fixes the assumption for isTez/isLLAP. But we still need HIVE-15508 for
exact memory tracking.
> LLAP: GroupByOperator flushes hash table too frequently
> -------------------------------------------------------
>
> Key: HIVE-15565
> URL: https://issues.apache.org/jira/browse/HIVE-15565
> Project: Hive
> Issue Type: Bug
> Components: llap
> Reporter: Rajesh Balamohan
> Assignee: Rajesh Balamohan
> Priority: Minor
> Fix For: 2.2.0
>
> Attachments: HIVE-15565.1.patch
>
>
> {{GroupByOperator::isTez}} would be true in LLAP mode. Current memory
> computations can go wrong with {{isTez}} checks in {{GroupByOperator}}. For
> e.g, in a LLAP instance with Xmx128G and 12 executors, it would start
> flushing hash table for every record once it reaches around 42GB
> (hive.tez.container.size=7100, hive.map.aggr.hash.percentmemory=0.5).
> {noformat}
> 2017-01-08T23:40:21,339 INFO [TezTaskRunner
> (1480722417364_1922_7_03_000004_1)]
> org.apache.hadoop.hive.ql.exec.GroupByOperator: Hash Table flushed: new size
> = 0
> 2017-01-08T23:40:21,339 INFO [TezTaskRunner
> (1480722417364_1922_7_03_000012_1)]
> org.apache.hadoop.hive.ql.exec.GroupByOperator: Hash Table flushed: new size
> = 0
> 2017-01-08T23:40:21,339 INFO [TezTaskRunner
> (1480722417364_1922_7_03_000004_1)]
> org.apache.hadoop.hive.ql.exec.GroupByOperator: Hash Tbl flush: #hash table =
> 1
> 2017-01-08T23:40:21,339 INFO [TezTaskRunner
> (1480722417364_1922_7_03_000012_1)]
> org.apache.hadoop.hive.ql.exec.GroupByOperator: Hash Tbl flush: #hash table =
> 1
> {noformat}
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