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Pavel Pereslegin commented on IGNITE-11584:
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Additional notes on risks and assumptions:
# These changes were checked for memory leaks in {{testSimpleRebalancing}} and
{{testComplexRebalancing}} tests, using the following
[method|https://github.com/apache/ignite/commit/472d5aa17de31a0eca780a61f9a655ec20a77e25#diff-50ffa3c92f2815b7e31d1dcc22ec6cc1R2329].
# If WAL is enabled during rebalancing, it is possible that after a node
failure, the WAL recovery procedure may add unused rows into the page memory.
Expecting partition eviction in such a case.
# Rebalancing of "staled" keys can run slower, due to rollbacks. Rollback
occurred when the node already has the key with a newer version - in this case,
preloader will remove a "pre-created" data row from the page memory.
> Implement batch insertion of new cache entries in FreeList to improve
> rebalancing
> ---------------------------------------------------------------------------------
>
> Key: IGNITE-11584
> URL: https://issues.apache.org/jira/browse/IGNITE-11584
> Project: Ignite
> Issue Type: Sub-task
> Affects Versions: 2.7
> Reporter: Pavel Pereslegin
> Assignee: Pavel Pereslegin
> Priority: Major
> Labels: iep-32
> Fix For: 2.8
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Main goals:
> * Implement batch insert operation into FreeList - insert several data rows
> at once
> * Use batch insertion in the preloader
>
> Implementation notes:
> # Preloader cannot lock multiple cache entries at once, because this may
> lead to a deadlock with concurrent batch updates. Therefore, it pre-creates
> batch of data rows in the page memory, and then sequentially initializes the
> cache entries one by one.
> # Batch writing of data rows into data pages uses the free list as usual
> because other approaches increase memory fragmentation (for example, using
> only "reuse" or "most free" buckets).
> # Eviction tracker assumes that only data pages with "heads" of fragmented
> data row are tracked, so all other fragments of large data row should be
> written on separate data pages (without other data rows which may cause page
> tracking).
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