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HADOOP-11466. FastByteComparisons: do not use UNSAFE_COMPARER on the SPARC architecture because it is slower there (Suman Somasundar via Colin P. McCabe)

This commit is contained in:
Colin Patrick Mccabe 2015-01-21 16:33:02 -08:00
parent a0521bc83a
commit ee7d22e90c
2 changed files with 24 additions and 1 deletions
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4
hadoop-common-project/hadoop-common/CHANGES.txt
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@ -737,6 +737,10 @@ Release 2.7.0 - UNRELEASED
HADOOP-11327. BloomFilter#not() omits the last bit, resulting in an
incorrect filter (Eric Payne via jlowe)
HADOOP-11466. FastByteComparisons: do not use UNSAFE_COMPARER on the SPARC
architecture because it is slower there (Suman Somasundar via Colin P.
McCabe)
Release 2.6.0 - 2014-11-18
INCOMPATIBLE CHANGES

21
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/FastByteComparisons.java
View File

@ -24,6 +24,9 @@ import java.security.PrivilegedAction;
import sun.misc.Unsafe;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import com.google.common.primitives.Longs;
import com.google.common.primitives.UnsignedBytes;
@ -33,6 +36,7 @@ import com.google.common.primitives.UnsignedBytes;
* class to be able to compare arrays that start at non-zero offsets.
*/
abstract class FastByteComparisons {
static final Log LOG = LogFactory.getLog(FastByteComparisons.class);
/**
* Lexicographically compare two byte arrays.
@ -71,6 +75,13 @@ abstract class FastByteComparisons {
* implementation if unable to do so.
*/
static Comparer<byte[]> getBestComparer() {
if (System.getProperty("os.arch").equals("sparc")) {
if (LOG.isTraceEnabled()) {
LOG.trace("Lexicographical comparer selected for "
+ "byte aligned system architecture");
}
return lexicographicalComparerJavaImpl();
}
try {
Class<?> theClass = Class.forName(UNSAFE_COMPARER_NAME);
@ -78,8 +89,16 @@ abstract class FastByteComparisons {
@SuppressWarnings("unchecked")
Comparer<byte[]> comparer =
(Comparer<byte[]>) theClass.getEnumConstants()[0];
if (LOG.isTraceEnabled()) {
LOG.trace("Unsafe comparer selected for "
+ "byte unaligned system architecture");
}
return comparer;
} catch (Throwable t) { // ensure we really catch *everything*
if (LOG.isTraceEnabled()) {
LOG.trace(t.getMessage());
LOG.trace("Lexicographical comparer selected");
}
return lexicographicalComparerJavaImpl();
}
}
@ -234,4 +253,4 @@ abstract class FastByteComparisons {
}
}
}
}
}