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https://issues.apache.org/jira/browse/IGNITE-7931?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16422978#comment-16422978
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Nikolay Izhikov commented on IGNITE-7931:
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TeamCity -
https://ci.ignite.apache.org/viewLog.html?buildId=1172948&tab=buildResultsDiv&buildTypeId=IgniteTests24Java8_RunAll
> Wrong arguments for ConcurrentHashMap
> --------------------------------------
>
> Key: IGNITE-7931
> URL: https://issues.apache.org/jira/browse/IGNITE-7931
> Project: Ignite
> Issue Type: Improvement
> Reporter: Ivan Fedotov
> Assignee: Ivan Fedotov
> Priority: Trivial
> Fix For: 2.5
>
>
> When creating ConcurrentHashMap:
> {code:java|title=BinaryUtils.java}
> new ConcurrentHashMap<>(U.capacity((map).size()));{code}
> [1], [2] `U.capacity` returns capacity that is sufficient to keep the map
> from being resized. In ConcurrentHashMap this is unnecessary because
> recalculation already performs in the constructor.
> Similar problem in GridConcurrentHashSet because inside it implements
> ConcurrentHashMap:
> {code:java|title=DataStreamerImpl.java}
> keys = new GridConcurrentHashSet<>(entries.size(),
> U.capacity(entries.size()), 1);{code}
> [3],[4] result of `U.capacity` is passed as `loadFactor` value. When
> loadFactor == U.capacity, initial size of table is 1.
> This leads to performance penalty due to rehashing of internal map.
>
> [1][https://github.com/1vanan/ignite/blob/master/modules/core/src/main/java/org/apache/ignite/internal/binary/BinaryUtils.java#L670]
> [2][https://github.com/1vanan/ignite/blob/master/modules/core/src/main/java/org/apache/ignite/internal/binary/BinaryUtils.java#L688|https://github.com/1vanan/ignite/blob/master/modules/core/src/main/java/org/apache/ignite/internal/binary/BinaryUtils.java#L670]
> [3][https://github.com/apache/ignite/blob/master/modules/core/src/main/java/org/apache/ignite/internal/processors/datastreamer/DataStreamerImpl.java#L633]
> [4][https://github.com/apache/ignite/blob/master/modules/core/src/main/java/org/apache/ignite/internal/processors/datastreamer/DataStreamerImpl.java#L574]
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