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https://issues.apache.org/jira/browse/HIVE-21686?focusedWorklogId=241449&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-241449
]
ASF GitHub Bot logged work on HIVE-21686:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 14/May/19 02:17
Start Date: 14/May/19 02:17
Worklog Time Spent: 10m
Work Description: b-slim commented on pull request #626: [HIVE-21686]
ensure that memory allocator does not evict using brute …
URL: https://github.com/apache/hive/pull/626#discussion_r283602968
##########
File path: common/src/java/org/apache/hadoop/hive/conf/HiveConf.java
##########
@@ -4053,6 +4053,9 @@ private static void
populateLlapDaemonVarsSet(Set<String> llapDaemonVarsSetLocal
LLAP_ALLOCATOR_DEFRAG_HEADROOM("hive.llap.io.allocator.defrag.headroom",
"1Mb",
"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."),
+
LLAP_ALLOCATOR_MAX_FORCE_EVICTED("hive.llap.io.allocator.max.force.eviction",
"16Mb",
+ "How much bytes we can force evict before using free List discards
and/or burt force\n" +
Review comment:
did a reword let me know if you think it is still unclear.
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Issue Time Tracking
-------------------
Worklog Id: (was: 241449)
Time Spent: 3h (was: 2h 50m)
> 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.patch
>
> Time Spent: 3h
> 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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