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From "Hive QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-21686) Brute Force eviction can lead to a random uncontrolled eviction pattern.
Date Tue, 14 May 2019 05:59:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-21686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16839101#comment-16839101
] 

Hive QA commented on HIVE-21686:
--------------------------------



Here are the results of testing the latest attachment:
https://issues.apache.org/jira/secure/attachment/12968633/HIVE-21686.3.patch

{color:green}SUCCESS:{color} +1 due to 3 test(s) being added or modified.

{color:green}SUCCESS:{color} +1 due to 16011 tests passed

Test results: https://builds.apache.org/job/PreCommit-HIVE-Build/17202/testReport
Console output: https://builds.apache.org/job/PreCommit-HIVE-Build/17202/console
Test logs: http://104.198.109.242/logs/PreCommit-HIVE-Build-17202/

Messages:
{noformat}
Executing org.apache.hive.ptest.execution.TestCheckPhase
Executing org.apache.hive.ptest.execution.PrepPhase
Executing org.apache.hive.ptest.execution.YetusPhase
Executing org.apache.hive.ptest.execution.ExecutionPhase
Executing org.apache.hive.ptest.execution.ReportingPhase
{noformat}

This message is automatically generated.

ATTACHMENT ID: 12968633 - PreCommit-HIVE-Build

> Brute Force eviction can lead to a random uncontrolled eviction pattern.
> ------------------------------------------------------------------------
>
>                 Key: HIVE-21686
>                 URL: https://issues.apache.org/jira/browse/HIVE-21686
>             Project: Hive
>          Issue Type: Bug
>            Reporter: slim bouguerra
>            Assignee: slim bouguerra
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: Cache_hitrate_improvement.csv, HIVE-21686.2.patch, HIVE-21686.3.patch,
HIVE-21686.4.patch, HIVE-21686.patch
>
>          Time Spent: 3.5h
>  Remaining Estimate: 0h
>
> Current logic used by brute force eviction can lead to a perpetual random eviction pattern.
> For instance if the cache build a small pocket of free memory where the total size is
greater than incoming allocation request, the allocator will randomly evict block that fits
a particular size.
> This can happen over and over therefore all the eviction will be random.
> In Addition this random eviction will lead a leak in the linked list maintained by the
policy since it does not know anymore about what is evicted and what not.
> The improvement of this patch is very substantial  to TPC-DS benchmark. I have tested
it with 10TB scale 9 llap nodes and 32GB cache size per node.  The patch has showed very noticeable
difference in the Hit rate for raw number  [^Cache_hitrate_improvement.csv] 



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