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https://issues.apache.org/jira/browse/CASSANDRA-5549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13838627#comment-13838627
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Vijay commented on CASSANDRA-5549:
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{quote}
Without switch lock, we won't have anything preventing writes coming through
when we're over-burdened with memory use by memtables.
{quote}
I should be missing something, how does the switch RW Lock to a kind of CAS
operation change this schematics?
Are we talking about additional requirement/enhancements to this ticket?
{quote}
When we flush a memtable we release permits equal to the estimated size of
each RM
{quote}
IMHO, that might not be good enough since Java's memory over head is not
considered. And calculating the object size is not cheap either....
> Remove Table.switchLock
> -----------------------
>
> Key: CASSANDRA-5549
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5549
> Project: Cassandra
> Issue Type: Bug
> Reporter: Jonathan Ellis
> Assignee: Vijay
> Labels: performance
> Fix For: 2.1
>
> Attachments: 5549-removed-switchlock.png, 5549-sunnyvale.png
>
>
> As discussed in CASSANDRA-5422, Table.switchLock is a bottleneck on the write
> path. ReentrantReadWriteLock is not lightweight, even if there is no
> contention per se between readers and writers of the lock (in Cassandra,
> memtable updates and switches).
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