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https://issues.apache.org/jira/browse/CASSANDRA-8630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14702720#comment-14702720
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Benedict edited comment on CASSANDRA-8630 at 8/19/15 9:06 AM:
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bq. He also added Constructor is private, maybe a rate limiter with a huge
rate?.
Sorry, missed that :)
bq. How would we handle files bigger than Integer.MAX_SIZE?
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.
was (Author: benedict):
bq. He also added Constructor is private, maybe a rate limiter with a huge
rate?.
Sorry, missed that :)
bq. How would we handle files bigger than Integer.MAX_SIZE?
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.
> 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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