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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Work logged] (HIVE-21686) Brute Force eviction can lead to a random uncontrolled eviction pattern.
Date Mon, 13 May 2019 20:47:01 GMT


ASF GitHub Bot logged work on HIVE-21686:

                Author: ASF GitHub Bot
            Created on: 13/May/19 20:46
            Start Date: 13/May/19 20:46
    Worklog Time Spent: 10m 
      Work Description: odraese commented on pull request #626: [HIVE-21686] ensure that memory
allocator does not evict using brute …

 File path: common/src/java/org/apache/hadoop/hive/conf/
 @@ -4053,6 +4053,9 @@ private static void populateLlapDaemonVarsSet(Set<String> llapDaemonVarsSetLocal
         "How much of a headroom to leave to allow allocator more flexibility to defragment.\n"
         "The allocator would further cap it to a fraction of total memory."),
+        "How much bytes we can force evict before using free List discards and/or burt force\n"
 Review comment:
   How much bytes -> how many bytes
   burt force -> brute force
   (general: the description isn't very helpful w/o knowing impl. details)
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Issue Time Tracking

    Worklog Id:     (was: 241286)
    Time Spent: 40m  (was: 0.5h)

> Brute Force eviction can lead to a random uncontrolled eviction pattern.
> ------------------------------------------------------------------------
>                 Key: HIVE-21686
>                 URL:
>             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.patch
>          Time Spent: 40m
>  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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