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https://issues.apache.org/jira/browse/CASSANDRA-1930?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12980207#action_12980207
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Hudson commented on CASSANDRA-1930:
-----------------------------------
Integrated in Cassandra-0.7 #151 (See
[https://hudson.apache.org/hudson/job/Cassandra-0.7/151/])
> db.Table flusherLock write lock fairness policy is sub-optimal
> --------------------------------------------------------------
>
> Key: CASSANDRA-1930
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1930
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Kelvin Kakugawa
> Assignee: Kelvin Kakugawa
> Fix For: 0.7.1
>
> Attachments: CASSANDRA-1930.0001.patch
>
>
> h4. scenario:
> 1) high write throughput cluster
> 2) external services adding material cpu contention
> h4. symptoms:
> The row mutation stage falls *very* behind.
> h4. cause:
> ReentrantReadWriteLock's fair policy causes write lock acquisition / release
> to require a material amount of CPU time.
> h4. summary:
> When there are other services contending for the CPU, the RRW lock's fair
> policy causes write lock acquisition / release to take enough time to
> eventually put threads waiting for read lock acquisition very behind. We
> repro'd this scenario by reducing the scope of the write lock to: 1 boolean
> check, 1 boolean assignment, and 1 db.Memtable instantiation (itself, just: 2
> variable assignments) w/ the same performance. Modifying the fairness policy
> to be the default policy allowed the row mutation stage to keep up.
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