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https://issues.apache.org/jira/browse/HADOOP-8926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13476945#comment-13476945
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Hadoop QA commented on HADOOP-8926:
-----------------------------------
{color:green}+1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12549285/crc32-faster%2Breadable.patch
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:green}+1 tests included{color}. The patch appears to include 1 new
or modified test files.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 javadoc{color}. The javadoc tool did not generate any
warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 1.3.9) warnings.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:green}+1 core tests{color}. The patch passed unit tests in
hadoop-common-project/hadoop-common.
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-HADOOP-Build/1632//testReport/
Console output:
https://builds.apache.org/job/PreCommit-HADOOP-Build/1632//console
This message is automatically generated.
> 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
> 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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