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https://issues.apache.org/jira/browse/HADOOP-8926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13477863#comment-13477863
]
Hudson commented on HADOOP-8926:
--------------------------------
Integrated in Hadoop-Mapreduce-trunk #1228 (See
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk/1228/])
HADOOP-8926. hadoop.util.PureJavaCrc32 cache hit-ratio is low for static
data (Gopal V via bobby) (Revision 1399005)
Result = FAILURE
bobby : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1399005
Files :
* /hadoop/common/trunk/hadoop-common-project/hadoop-common/CHANGES.txt
*
/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/PureJavaCrc32.java
*
/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/PureJavaCrc32C.java
*
/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestPureJavaCrc32.java
> hadoop.util.PureJavaCrc32 cache hit-ratio is low for static data
> ----------------------------------------------------------------
>
> Key: HADOOP-8926
> URL: https://issues.apache.org/jira/browse/HADOOP-8926
> Project: Hadoop Common
> Issue Type: Improvement
> Components: util
> Affects Versions: 2.0.3-alpha
> Environment: Ubuntu 10.10 i386
> Reporter: Gopal V
> Assignee: Gopal V
> Priority: Trivial
> Labels: optimization
> Fix For: 3.0.0, 2.0.3-alpha
>
> Attachments: crc32-faster+readable.patch, crc32-faster+test.patch,
> pure-crc32-cache-hit.patch
>
>
> While running microbenchmarks for HDFS write codepath, a significant part of
> the CPU fraction was consumed by the DataChecksum.update().
> The attached patch converts the static arrays in CRC32 into a single linear
> array for a performance boost in the inner loop.
> milli-seconds for 1Gig (16400 loop over a 64kb chunk)
> || platform || original || cache-aware || improvement ||
> | x86 | 3894 | 2304 | 40.83 |
> | x86_64 | 2131 | 1826 | 14 |
> The performance improvement on x86 is rather larger than the 64bit case, due
> to the extra register/stack pressure caused by the static arrays.
> A closer analysis of the PureJavaCrc32 JIT code shows the following assembly
> fragment
> {code}
> 0x40f1e345: mov $0x184,%ecx
> 0x40f1e34a: mov 0x4415b560(%ecx),%ecx ;*getstatic T8_5
> ; - PureJavaCrc32::update@95 (line 61)
> ; {oop('PureJavaCrc32')}
> 0x40f1e350: mov %ecx,0x2c(%esp)
> {code}
> Basically, the static variables T8_0 through to T8_7 are being spilled to the
> stack because of register pressure. The x86_64 case has a lower likelihood of
> such pessimistic JIT code due to the increased number of registers.
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