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https://issues.apache.org/jira/browse/CASSANDRA-17655?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17577603#comment-17577603
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Brad Schoening commented on CASSANDRA-17655:
--------------------------------------------
Agreed, we need a heap dump or other sample of the problem to determine what
type of objects are being allocated in the humongous region. If is something
like the partition summary table, maybe there is an opportunity to move it off
heap or tweak the data structure so it doesn't require a humongous allocation.
> Prevent JVM Humongous allocations
> ---------------------------------
>
> Key: CASSANDRA-17655
> URL: https://issues.apache.org/jira/browse/CASSANDRA-17655
> Project: Cassandra
> Issue Type: Bug
> Reporter: Brad Schoening
> Priority: Normal
>
> Several articles on Cassandra note that certain workloads, especially large
> partitions, can cause humongous allocations in Java, which can be reduced,
> but not always eliminated by increasing RegionSize. RegionSize max is 32MB.
> Humongous allocations are an undesirable performance issue because new
> objects get directly allocated in old space.
> Below is a sample message seen in the gc.log
> 2022-05-23T18:46:58.743+0800: 3758624.170: [GC pause (G1 Humongous
> Allocation) (young) (initial-mark) 3758624.171: [G1Ergonomics (CSet
> Construction) start choosing CSet, _pending_cards: 56725, predicted base
> time: 39.83 ms, remaining time: 160.17 ms, target pause time: 200.00 ms]
> Instead of Cassandra users tuning RegionSize manually, a better solution
> would be for Cassandra to limit the size of allocations, or consider moving
> humongous allocations off heap.
>
> References
> [https://docs.oracle.com/en/java/javase/11/gctuning/garbage-first-g1-garbage-collector1.html#GUID-D74F3CC7-CC9F-45B5-B03D-510AEEAC2DAC]
> [https://stevenlacerda.medium.com/identifying-and-fixing-humongous-allocations-in-cassandra-bf46444cec41]
> https://krzysztofslusarski.github.io/2020/11/10/humongous.html
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