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https://issues.apache.org/jira/browse/CASSANDRA-6949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13969709#comment-13969709
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Benedict commented on CASSANDRA-6949:
-------------------------------------
I assume the only real risk with reverting is that if there are no reads we can
get uncontrolled growth of the 2i?
> Performance regression in tombstone heavy workloads
> ---------------------------------------------------
>
> Key: CASSANDRA-6949
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6949
> Project: Cassandra
> Issue Type: Bug
> Reporter: Jeremiah Jordan
> Assignee: Sam Tunnicliffe
> Attachments:
> 0001-Remove-expansion-of-RangeTombstones-to-delete-from-2.patch, 6949.txt
>
>
> CASSANDRA-5614 causes a huge performance regression in tombstone heavy
> workloads. The isDeleted checks here cause a huge CPU overhead:
> https://github.com/apache/cassandra/blob/cassandra-2.0/src/java/org/apache/cassandra/db/AtomicSortedColumns.java#L189-L196
> An insert workload which does perfectly fine on 1.2, pegs CPU use at 100% on
> 2.0, with all of the mutation threads sitting in that loop. For example:
> {noformat}
> "MutationStage:20" daemon prio=10 tid=0x00007fb1c4c72800 nid=0x2249 runnable
> [0x00007fb1b0330000]
> java.lang.Thread.State: RUNNABLE
> at org.apache.cassandra.db.marshal.BytesType.bytesCompare(BytesType.java:45)
> at org.apache.cassandra.db.marshal.UTF8Type.compare(UTF8Type.java:34)
> at org.apache.cassandra.db.marshal.UTF8Type.compare(UTF8Type.java:26)
> at
> org.apache.cassandra.db.marshal.AbstractType.compareCollectionMembers(AbstractType.java:267)
> at
> org.apache.cassandra.db.marshal.AbstractCompositeType.compare(AbstractCompositeType.java:85)
> at
> org.apache.cassandra.db.marshal.AbstractCompositeType.compare(AbstractCompositeType.java:35)
> at
> org.apache.cassandra.db.RangeTombstoneList.searchInternal(RangeTombstoneList.java:253)
> at
> org.apache.cassandra.db.RangeTombstoneList.isDeleted(RangeTombstoneList.java:210)
> at org.apache.cassandra.db.DeletionInfo.isDeleted(DeletionInfo.java:136)
> at org.apache.cassandra.db.DeletionInfo.isDeleted(DeletionInfo.java:123)
> at
> org.apache.cassandra.db.AtomicSortedColumns.addAllWithSizeDelta(AtomicSortedColumns.java:193)
> at org.apache.cassandra.db.Memtable.resolve(Memtable.java:194)
> at org.apache.cassandra.db.Memtable.put(Memtable.java:158)
> at org.apache.cassandra.db.ColumnFamilyStore.apply(ColumnFamilyStore.java:890)
> at org.apache.cassandra.db.Keyspace.apply(Keyspace.java:368)
> at org.apache.cassandra.db.Keyspace.apply(Keyspace.java:333)
> at org.apache.cassandra.db.RowMutation.apply(RowMutation.java:201)
> at
> org.apache.cassandra.db.RowMutationVerbHandler.doVerb(RowMutationVerbHandler.java:56)
> at
> org.apache.cassandra.net.MessageDeliveryTask.run(MessageDeliveryTask.java:60)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:744)
> {noformat}
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