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Posted to commits@cassandra.apache.org by "Benedict Elliott Smith (Jira)" <ji...@apache.org> on 2020/03/04 11:46:00 UTC
[jira] [Commented] (CASSANDRA-15367) Memtable memory allocations
may deadlock
[ https://issues.apache.org/jira/browse/CASSANDRA-15367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17051130#comment-17051130 ]
Benedict Elliott Smith commented on CASSANDRA-15367:
----------------------------------------------------
Sorry for the delay on this, I've been trying to figure out what's wrong with CircleCI for 3.0 and 3.11, but have given up. It appears the issues occur on HEAD for both as well.
[3.0|https://github.com/belliottsmith/cassandra/tree/15367-3.0] [3.0ci|https://circleci.com/workflow-run/b6396d79-d2bb-42a1-a76f-805715e896de] [3.0-HEADci|https://circleci.com/workflow-run/759d8331-7e2f-431f-8161-847fe46af4d3]
[3.11|https://github.com/belliottsmith/cassandra/tree/15367-311] [3.11ci|https://circleci.com/workflow-run/7c74fea5-3730-44bf-bd62-5d112cf974d4] [3.11-HEADci|https://circleci.com/workflow-run/72a173e0-713e-479d-b5db-9fd7e94eb3d6][trunk|https://github.com/belliottsmith/cassandra/tree/15367-trunk] [trunkci|https://circleci.com/workflow-run/b2b24c56-d191-4923-9f66-b05036d62ea1]
I will commit tomorrow after double checking the test failures are consistent and assuming you don't say otherwise.
> 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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