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https://issues.apache.org/jira/browse/HBASE-20542?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16516625#comment-16516625
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Ted Yu commented on HBASE-20542:
--------------------------------
When I ran the test locally with patch, I saw the following in test output:
{code}
2018-06-18 20:43:32,244 ERROR [Time-limited test] regionserver.HRegion(1249):
Asked to modify this region's
(foobar,,1529379812191.c0c4ada07a3a9905699278a1b1fd63ff.) memStoreSizing to a
negative value which is incorrect. Current memStoreSizing=0, delta=-32
java.lang.Exception
at
org.apache.hadoop.hbase.regionserver.HRegion.checkNegativeMemStoreDataSize(HRegion.java:1249)
at
org.apache.hadoop.hbase.regionserver.HRegion.incMemStoreSize(HRegion.java:1229)
at
org.apache.hadoop.hbase.regionserver.RegionServicesForStores.addMemStoreSize(RegionServicesForStores.java:61)
at
org.apache.hadoop.hbase.regionserver.CompactionPipeline.swap(CompactionPipeline.java:153)
at
org.apache.hadoop.hbase.regionserver.CompactingMemStore.swapCompactedSegments(CompactingMemStore.java:332)
at
org.apache.hadoop.hbase.regionserver.MemStoreCompactor.doCompaction(MemStoreCompactor.java:177)
at
org.apache.hadoop.hbase.regionserver.MemStoreCompactor.start(MemStoreCompactor.java:110)
at
org.apache.hadoop.hbase.regionserver.CompactingMemStore.inMemoryCompaction(CompactingMemStore.java:459)
at
org.apache.hadoop.hbase.regionserver.CompactingMemStore.flushInMemory(CompactingMemStore.java:439)
at
org.apache.hadoop.hbase.regionserver.TestCompactingToCellFlatMapMemStore.testTimeRange(TestCompactingToCellFlatMapMemStore.java:409)
at
org.apache.hadoop.hbase.regionserver.TestCompactingToCellFlatMapMemStore.testTimeRangeAfterCompaction(TestCompactingToCellFlatMapMemStore.java:374)
{code}
> Better heap utilization for IMC with MSLABs
> -------------------------------------------
>
> Key: HBASE-20542
> URL: https://issues.apache.org/jira/browse/HBASE-20542
> Project: HBase
> Issue Type: Sub-task
> Reporter: Eshcar Hillel
> Assignee: Eshcar Hillel
> Priority: Major
> Attachments: HBASE-20542.branch-2.001.patch, run.sh, workloada,
> workloadc, workloadx, workloady
>
>
> Following HBASE-20188 we realized in-memory compaction combined with MSLABs
> may suffer from heap under-utilization due to internal fragmentation. This
> jira presents a solution to circumvent this problem. The main idea is to have
> each update operation check if it will cause overflow in the active segment
> *before* it is writing the new value (instead of checking the size after the
> write is completed), and if it is then the active segment is atomically
> swapped with a new empty segment, and is pushed (full-yet-not-overflowed) to
> the compaction pipeline. Later on the IMC deamon will run its compaction
> operation (flatten index/merge indices/data compaction) in the background.
> Some subtle concurrency issues should be handled with care. We next elaborate
> on them.
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