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https://issues.apache.org/jira/browse/CASSANDRA-8630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14724092#comment-14724092
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Benedict commented on CASSANDRA-8630:
-------------------------------------
I've pushed a version with a few suggestions, and a bug fix, in decreasing
order of note:
* {{MappedRegions.close}} now always calls {{channel.close}}, and returns any
error thrown by it
* Removed the {{readBytes}} method entirely, since it doesn't appear to offer
anything {{readFully}} and, transitively, {{ByteBufferUtil.read}}, doesn't
(correct me if I'm wrong...?)
** Simplified {{readFully}} while we're here
* Moved some of the {{close}} methods to the new {{Throwables.perform}} API to
make their behaviour more robust
* Replaced {{AssertionError}} with {{UnsupportedOperationException}} where
suitable
* Removed {{IOException}} from the throws clause of close, so no need to
introduce the new {{closeQuietly}} calls
* Removed the (as commented in TODO) unnecessary
{{BufferedSegmentedFile.createReader}}
* {{ChecksummedDataInput}} extends
{{RandomAccessReader.RandomAccessReaderWithOwnChannel}}
* Removed / standardised EOF behaviour for RAR and CRAR
Let me know what you think, and we can squash/commit.
bq. how picky the platform is about timing on DirectBuffer unmapping etc.
[~JoshuaMcKenzie]: is this wrt file rename / deletion, or wrt closing the
channel? My understanding was the former, in which case any such problem would
indicate a severe bug with 2.2+ (unless snapshots are involved, but don't think
we even try to handle that), and shouldn't be affected by this patch.
Absolutely no harm running the tests, of course.
> 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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