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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-8630) Faster sequential IO (on compaction, streaming, etc)
Date Wed, 19 Aug 2015 09:07:47 GMT

    [ 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:
--------------------------------------------------------------

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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