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https://issues.apache.org/jira/browse/HIVE-21686?focusedWorklogId=241297&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-241297
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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 …
URL: https://github.com/apache/hive/pull/626#discussion_r283427735
##########
File path:
llap-server/src/java/org/apache/hadoop/hive/llap/cache/BuddyAllocator.java
##########
@@ -65,19 +83,26 @@
private final long maxSize;
private final boolean isDirect;
private final boolean isMapped;
+ private final int maxForcedEvictionSize;
private final Path cacheDir;
// These are only used for tests.
private boolean enableDefragShortcut = true, oomLogging = true;
// We don't know the acceptable size for Java array, so we'll use 1Gb
boundary.
// That is guaranteed to fit any maximum allocation.
- private static final int MAX_ARENA_SIZE = 1024*1024*1024;
+ private static final int MAX_ARENA_SIZE = 1024 * 1024 * 1024;
// Don't try to operate with less than MIN_SIZE allocator space, it will
just give you grief.
- private static final int MIN_TOTAL_MEMORY_SIZE = 64*1024*1024;
+ private static final int MIN_TOTAL_MEMORY_SIZE = 64 * 1024 * 1024;
// Maximum reasonable defragmentation headroom. Mostly kicks in on very
small caches.
private static final float MAX_DEFRAG_HEADROOM_FRACTION = 0.01f;
-
+ /**
+ * Max number of attempts to try allocations before giving up and move to
forced evictions or/and freelist/brut
Review comment:
brut -> brute
Also, having some comment, explaining the forced eviction (brute force
discards) or freeList would help.
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Issue Time Tracking
-------------------
Worklog Id: (was: 241297)
Time Spent: 2h 20m (was: 2h 10m)
> 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: 2h 20m
> 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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