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From "Vijay (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-5549) Remove Table.switchLock
Date Wed, 04 Dec 2013 05:51:36 GMT


Vijay commented on CASSANDRA-5549:

Without switch lock, we won't have anything preventing writes coming through when we're over-burdened
with memory use by memtables.
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?

 When we flush a memtable we release permits equal to the estimated size of each RM
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:
>             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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