cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8630) Faster sequential IO (on compaction, streaming, etc)
Date Tue, 18 Aug 2015 21:27:48 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14702017#comment-14702017
] 

Ariel Weisberg commented on CASSANDRA-8630:
-------------------------------------------

Some more things I noticed

* RandomAccessReader.readBytes could allocate the buffer and then invoke the superclass read
method
* MemoryInputStream.reBuffer is allegedly not tested
* RandomAccessReader.reBuffer has two cases that aren't tested, if (limit > fileLength)
and in the loop if (n < 0)
* RandomAccessReader.open(ByteBuffer, String, long) usage of checked cast seems like it would
also limit to 2 gig files?
* Not sure about the first checked cast in reBufferMmap, if it saturated the min would still
work, and you would be able to do it multiple times to get to the next entry so no reason
to throw an exception?

Test coverage looks excellent on the things you worked on.

What's the business with the missing segments? How does that happen and how often? Just wondering
if going to the buffer pool for that makes sense.

> 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)



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message