[CASSANDRA-8630] Faster sequential IO (on compaction, streaming, etc)

• Type: Improvement
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 3.0.0 rc1
• Component/s: Legacy/Tools
• Labels: compaction performance
• Assignee: Stefania Alborghetti
• Reporter: Oleg Anastasyev

Authors

Stefania Alborghetti

Reviewers

Ariel Weisberg

• Created: 15/Jan/15 18:45
• Updated: 16/Apr/19 09:31
• Resolved: 10/Sep/15 13:32

Description

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)

Issue Links

• links to: 3.0 patch
• links to: coverity fix