Details
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Improvement
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Status: Open
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Low
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Resolution: Unresolved
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None
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None
Description
I had to use sstablesplit tool intensively to split some really huge sstables. The tool is painfully slow as it does compaction in one single thread.
I have just found that one one of my machines the tool has crashed when I was almost done with 152Gb sstable (!!!).
INFO 16:59:22,342 Writing Memtable-compactions_in_progress@1948660572(0/0 serialized/live bytes, 1 ops) INFO 16:59:22,352 Completed flushing /cassandra-data/disk1/system/compactions_in_progress/system-compactions_in_progress-jb-79242-Data.db (42 bytes) for commitlog position ReplayPosition(segmentId=1413904450653, position=69178) Exception in thread "main" java.lang.OutOfMemoryError: GC overhead limit exceeded at java.nio.HeapByteBuffer.duplicate(HeapByteBuffer.java:107) at org.apache.cassandra.utils.ByteBufferUtil.readBytes(ByteBufferUtil.java:586) at org.apache.cassandra.utils.ByteBufferUtil.readBytesWithShortLength(ByteBufferUtil.java:596) at org.apache.cassandra.db.marshal.AbstractCompositeType.compare(AbstractCompositeType.java:61) at org.apache.cassandra.db.marshal.AbstractCompositeType.compare(AbstractCompositeType.java:36) at org.apache.cassandra.db.RangeTombstoneList$InOrderTester.isDeleted(RangeTombstoneList.java:751) at org.apache.cassandra.db.DeletionInfo$InOrderTester.isDeleted(DeletionInfo.java:422) at org.apache.cassandra.db.DeletionInfo$InOrderTester.isDeleted(DeletionInfo.java:403) at org.apache.cassandra.db.ColumnFamily.hasIrrelevantData(ColumnFamily.java:489) at org.apache.cassandra.db.compaction.PrecompactedRow.removeDeleted(PrecompactedRow.java:66) at org.apache.cassandra.db.compaction.PrecompactedRow.<init>(PrecompactedRow.java:85) at org.apache.cassandra.db.compaction.CompactionController.getCompactedRow(CompactionController.java:196) at org.apache.cassandra.db.compaction.CompactionIterable$Reducer.getReduced(CompactionIterable.java:74) at org.apache.cassandra.db.compaction.CompactionIterable$Reducer.getReduced(CompactionIterable.java:55) at org.apache.cassandra.utils.MergeIterator$OneToOne.computeNext(MergeIterator.java:204) at com.google.common.collect.AbstractIterator.tryToComputeNext(AbstractIterator.java:143) at com.google.common.collect.AbstractIterator.hasNext(AbstractIterator.java:138) at org.apache.cassandra.db.compaction.CompactionTask.runWith(CompactionTask.java:154) at org.apache.cassandra.io.util.DiskAwareRunnable.runMayThrow(DiskAwareRunnable.java:48) at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:28) at org.apache.cassandra.db.compaction.CompactionTask.executeInternal(CompactionTask.java:60) at org.apache.cassandra.db.compaction.AbstractCompactionTask.execute(AbstractCompactionTask.java:59) at org.apache.cassandra.db.compaction.SSTableSplitter.split(SSTableSplitter.java:38) at org.apache.cassandra.tools.StandaloneSplitter.main(StandaloneSplitter.java:150)
This has triggered my desire to see what memory settings are used for JVM running the tool...and I have found that it runs with default Java settings (no settings at all).
I have tried to apply the settings from C* itself and this resulted in over 40% speed increase. It went from ~5Mb/s to 7Mb/s - from the compressed output perspective. I believe this is mostly due to concurrent GC. I see my CPU usage has increased to ~200%. But this is fine, this is an offline tool, the node is down anyway. I know that concurrent GC (at least something like -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled) normally improves the performance of even primitive single-threaded heap-intensive Java programs.
I think it should be acceptable to apply the server JVM settings to this tool.