Suman Somasundar created HADOOP-11466:
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Summary: Newer Fast byte comparison is slower in SUN SPARC machines
Key: HADOOP-11466
URL: https://issues.apache.org/jira/browse/HADOOP-11466
Project: Hadoop Common
Issue Type: Improvement
Components: io, performance, util
Environment: Linux X86 and Solaris SPARC
Reporter: Suman Somasundar
Assignee: Suman Somasundar
Priority: Minor
One difference between Hadoop 2.x and Hadoop 1.x is a utility to compare two
byte arrays at coarser 8-byte granularity instead of at the byte-level. The
discussion at HADOOP-7761 says this fast byte comparison is somewhat faster for
longer arrays and somewhat slower for smaller arrays ( AVRO-939). In order to
do 8-byte reads on addresses not aligned to 8-byte boundaries, the patch uses
Unsafe.getLong. The problem is that this call is incredibly expensive on SPARC.
The reason is that the Studio compiler detects an unaligned pointer read and
handles this read in software. x86 supports unaligned reads, so there is no
penalty for this call on x86.
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