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https://issues.apache.org/jira/browse/CASSANDRA-8630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14700433#comment-14700433
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Ariel Weisberg commented on CASSANDRA-8630:
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Flight recording of 8630 with compression, hot packages
||Package|Sample Count|Percentage(%)||
|org.apache.cassandra.db.rows|1,577|25.403|
|org.apache.cassandra.utils|1,498|24.13|
|org.apache.cassandra.utils.btree|670|10.793|
|com.googlecode.concurrentlinkedhashmap|598|9.633|
|java.util|585|9.423|
|org.apache.cassandra.io.sstable|430|6.927|
|org.apache.cassandra.db.partitions|183|2.948|
|org.apache.cassandra.cache|162|2.61|
|org.apache.cassandra.io.util|139|2.239|
|org.apache.cassandra.db.rows.UnfilteredRowIterators$UnfilteredRowMergeIterator$$Lambda$93|77|1.24|
|org.apache.cassandra.db|74|1.192|
Flight recording trunk, hot packages
||Package|Sample Count|Percentage(%)||
|org.apache.cassandra.utils|1,771|26.732|
|org.apache.cassandra.db.rows|1,599|24.136|
|com.googlecode.concurrentlinkedhashmap|631|9.525|
|java.util|590|8.906|
|org.apache.cassandra.utils.btree|565|8.528|
|org.apache.cassandra.io.sstable|438|6.611|
|org.apache.cassandra.io.util|330|4.981|
|org.apache.cassandra.db.partitions|124|1.872|
|org.apache.cassandra.cache|121|1.826|
|org.apache.cassandra.io.sstable.format.big|105|1.585|
|org.apache.cassandra.db|102|1.54|
> Faster sequential IO (on compaction, streaming, etc)
> ----------------------------------------------------
>
> Key: CASSANDRA-8630
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8630
> Project: Cassandra
> Issue Type: Improvement
> Components: Core, Tools
> Reporter: Oleg Anastasyev
> Assignee: Stefania
> Labels: compaction, performance
> Fix For: 3.x
>
> Attachments: 8630-FasterSequencialReadsAndWrites.txt, cpu_load.png,
> flight_recorder_001_files.tar.gz, flight_recorder_002_files.tar.gz
>
>
> When node is doing a lot of sequencial IO (streaming, compacting, etc) a lot
> of CPU is lost in calls to RAF's int read() and DataOutputStream's write(int).
> This is because default implementations of readShort,readLong, etc as well as
> their matching write* are implemented with numerous calls of byte by byte
> read and write.
> This makes a lot of syscalls as well.
> A quick microbench shows than just reimplementation of these methods in
> either way gives 8x speed increase.
> A patch attached implements RandomAccessReader.read<Type> and
> SequencialWriter.write<Type> methods in more efficient way.
> I also eliminated some extra byte copies in CompositeType.split and
> ColumnNameHelper.maxComponents, which were on my profiler's hotspot method
> list during tests.
> A stress tests on my laptop show that this patch makes compaction 25-30%
> faster on uncompressed sstables and 15% faster for compressed ones.
> A deployment to production shows much less CPU load for compaction.
> (I attached a cpu load graph from one of our production, orange is niced CPU
> load - i.e. compaction; yellow is user - i.e. not compaction related tasks)
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