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https://issues.apache.org/jira/browse/CASSANDRA-8630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14702744#comment-14702744
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Stefania commented on CASSANDRA-8630:
-------------------------------------
The boundaries are gone. They are serialized in the summary but here we don't
need to keep backward compatibility as it will be recreated on the flight,
correct?
bq. In our SegmentedFileBuilder we can just map a segment on-demand (i.e.
whenever we build a SegmentedFile from it, we map any segments we need). We can
stick with the TreeMap<Long, ByteBuffer> (although tbh, I'd prefer we switch to
a paired long[] and ByteBuffer[], and perform binarySearch on the former to key
into the latter), it's just built with arbitrary boundaries.
I see what you mean now. So the segments will belong to the builder like the
channel. The reason I chose the tree map was to avoid changing the
CompressedRAR but it shouldn't take long to change the map to an array of
(Long, ByteBuffer) pairs. You prefer the binary search due to the cost of the
map?
> 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,
> mmaped_uncomp_hotspot.png
>
>
> 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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