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https://issues.apache.org/jira/browse/IMPALA-9221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17542656#comment-17542656
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Michael Smith commented on IMPALA-9221:
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Some realistic estimates for standard use cases are that we use
- ~3-40 hosts (maybe 200 for the very largest cluster, but not common)
- ~100s of reads in a query, to schedule file access; maybe 1000s for lots of
small files
> Optimize HashRing's map implementation
> --------------------------------------
>
> Key: IMPALA-9221
> URL: https://issues.apache.org/jira/browse/IMPALA-9221
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend
> Affects Versions: Impala 3.4.0
> Reporter: Joe McDonnell
> Assignee: Michael Smith
> Priority: Major
> Attachments: image-2022-05-26-10-23-57-678.png
>
>
> The hash ring used for consistent scheduling currently uses a std::map for
> the hash-to-IpAddr lookup. HashRing is heavy on reads, with writes only
> happening when executors come and go. There are some cases where we copy the
> HashRing.
> The standard map uses a large number of small allocations. This hurts cache
> performance, adds overhead, and also increases the cost of copying the
> structure. Something like boost's flat_map or Abseil's btree_map is likely to
> be more efficient.
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