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https://issues.apache.org/jira/browse/CASSANDRA-15367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17016398#comment-17016398
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Benedict Elliott Smith commented on CASSANDRA-15367:
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Correct, except perhaps the last part. There's no need to collect more than
one of these deadlocks to bring down the node. If there are no memtable
flushes already in progress, then no more flushes will ever occur, because they
must wait for all earlier operations to complete, including the deadlock. So
from this point on no Memtable memory will ever be released.
> Memtable memory allocations may deadlock
> ----------------------------------------
>
> Key: CASSANDRA-15367
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15367
> Project: Cassandra
> Issue Type: Bug
> Components: Local/Commit Log, Local/Memtable
> Reporter: Benedict Elliott Smith
> Assignee: Benedict Elliott Smith
> Priority: Normal
> Fix For: 4.0, 2.2.x, 3.0.x, 3.11.x
>
>
> * Under heavy contention, we guard modifications to a partition with a mutex,
> for the lifetime of the memtable.
> * Memtables block for the completion of all {{OpOrder.Group}} started before
> their flush began
> * Memtables permit operations from this cohort to fall-through to the
> following Memtable, in order to guarantee a precise commitLogUpperBound
> * Memtable memory limits may be lifted for operations in the first cohort,
> since they block flush (and hence block future memory allocation)
> With very unfortunate scheduling
> * A contended partition may rapidly escalate to a mutex
> * The system may reach memory limits that prevent allocations for the new
> Memtable’s cohort (C2)
> * An operation from C2 may hold the mutex when this occurs
> * Operations from a prior Memtable’s cohort (C1), for a contended partition,
> may fall-through to the next Memtable
> * The operations from C1 may execute after the above is encountered by those
> from C2
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