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From "Prasanth Jayachandran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-15598) DataChecksum calculate checksum is contented on hashtable synchronization
Date Wed, 11 Jul 2018 08:57:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-15598?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16539750#comment-16539750
] 

Prasanth Jayachandran commented on HADOOP-15598:
------------------------------------------------

Results from JMH microbenchmark. As we can see for bytebuffers of size >128 there is no
significant benefit as most of the time is spent on the chunk looping. But for smaller size,
the synchronization has significant impact. 

{noformat}
Benchmark                                               (size)  Mode  Cnt      Score     Error
 Units
ComputeChecksumBenchmark.benchmarkChecksumWithoutPatch       8  avgt   10     66.970 ±  
1.247  ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithoutPatch      16  avgt   10     91.524 ±  
2.141  ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithoutPatch      32  avgt   10    127.155 ±  
8.037  ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithoutPatch      64  avgt   10    233.941 ±  14.327
 ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithoutPatch     128  avgt   10    382.898 ±  
4.316  ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithoutPatch    1024  avgt   10   2707.026 ±  53.266
 ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithoutPatch    4096  avgt   10  11411.330 ± 181.900
 ns/op


Benchmark                                            (size)  Mode  Cnt      Score     Error
 Units
ComputeChecksumBenchmark.benchmarkChecksumWithPatch       8  avgt   10     27.948 ±   0.507
 ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithPatch      16  avgt   10     49.336 ±   1.212
 ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithPatch      32  avgt   10     96.344 ±   1.360
 ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithPatch      64  avgt   10    182.513 ±   2.553
 ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithPatch     128  avgt   10    356.205 ±   4.282
 ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithPatch    1024  avgt   10   2825.526 ±  31.177
 ns/op
ComputeChecksumBenchmark.benchmarkChecksumWithPatch    4096  avgt   10  12078.055 ± 262.343
 ns/op
{noformat}

> DataChecksum calculate checksum is contented on hashtable synchronization
> -------------------------------------------------------------------------
>
>                 Key: HADOOP-15598
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15598
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: common
>    Affects Versions: 3.2.0
>            Reporter: Prasanth Jayachandran
>            Priority: Major
>         Attachments: HADOOP-15598.1.patch, Screen Shot 2018-07-11 at 1.45.06 AM.png
>
>
> When profiling a multi-threaded hive streaming ingest, observed lock contention on java.util.Properties
getProperty() to check if os is "sparc". java.util.Properties internally uses HashTable. HashTable.get()
is synchronized method. In the test application, on a 30s profile with 64 threads ~40% CPU
time is spent on getProperty() contention. See attached snapshot.



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