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https://issues.apache.org/jira/browse/CASSANDRA-1954?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Ellis updated CASSANDRA-1954:
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Attachment: 1954-v2.txt
I like it. I renamed Frozen in v2 to PendingFlush (since with the new design
we accept writes to the old memtable even while maybeSwitch is running, so the
old implication of "once it's frozen nothing new gets added" is no longer true).
I do think we should move this to trunk though.
> Double-check or replace RRW memtable lock
> -----------------------------------------
>
> Key: CASSANDRA-1954
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1954
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Stu Hood
> Priority: Minor
> Attachments:
> 0001-Double-check-in-maybeSwitchMemtable-to-minimize-writeL.txt,
> 0001-Remove-flusherLock-readLock.patch, 1954-v2.txt
>
>
> {quote}...when a Memtable reaches its threshold, up to (all) N write threads
> will often notice, and race to acquire the writeLock in order to freeze the
> memtable. This means that we do way more writeLock acquisitions than we need
> to...{quote}
> See CASSANDRA-1930 for backstory, but adding double checking inside a read
> lock before trying to re-entrantly acquire the writelock would eliminate most
> of these excess writelock acquisitions.
> Alternatively, we should explore removing locking from these structures
> entirely, and replacing the writeLock acquisition with a per-memtable counter
> of active threads.
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